British insects: water beetles

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L. Watson and M. J. Dallwitz

Character list

#1. <Family nomenclature:>/

~ (‘alternatively’) is here used to indicate ‘sometimes not unreasonably included in or reduced to’.

#2. <Colloquial family names:>/

Adults

#3. Beetles <whether adults aquatic: water-beetles or land dwellers>/

1. terrestrial/

2. sub-aquatic/

3. aquatic/

For purposes of identification, the term ‘water beetle’ here includes assorted forms associated with wet habitats, in addition to true aquatics.

‘Aquatic’: living in water, with convincingly observed adaptations for respiring when submerged. ‘Sub-aquatic’: inhabiting wet places and apparently or supposedly surviving inundation, but sometimes not conspicuously adapted for respiring submerged. Assignment to these categories is sometimes unsatisfactory, because survival strategies in assorted ‘sub-aquatic’ families are either unknown, or are not detailed in the literature seen; and assignments are further complicated by (e.g.) Hydraenidae, in which the adults are genuinely aquatic but the larvae are easily drowned, and by Scirtidae, which combine terrestrial adults with aquatic larvae. The huge families Chrysomelidae and Curculionidae are really ‘terrestrial’, but adults associated with helophytic plants are often encountered floating or struggling in water.

#4. Beetles <adult locomotion>/

1. free-swimming and diving strongly, with the main thrust delivered by the specially adapted hind legs, moving clumsily on land/

2. surface swimmers with the main thrust delivered by the specialised middle legs, moving clumsily on land (Whirligigs)/

3. walking in water or free-swimming by conventional ambulatory motion of the legs, not diving strongly/

#5. Beetles <mode of locomotion in the water>/

1. ‘rowing’ and diving in water by parallel-simultaneous leg movements/

2. moving in the water by <conventional> alternate, walking leg movements <not rowing>/

#6. Beetles <aquatic, acquisition and transport of air>/

1. respiring under water via air which is collected posteriorly and stored directly under the elytra/

2. replenishing air for respiration beneath the elytra indirectly from that acquired and held in a ventral plastron <(q.v.), which may be visible as a bubble on the underside when submerged>/

‘Plastron’: in the present context, a pile of fine hydrofuge hairs on the ventral surface of many aquatic beetles, in which air is collected and stored to supply oxygen for respiration when they are submerged. Air transferred from the plastron to the water-tight space under the elytra is respired via the terminal pair of abdominal spiracles. The plastron, which is often conspicuous as a bubble on the underside of the submerged insect, is a characteristic feature of hydrophilid beetles, and distinguishes them from dytiscids. The latter also store air under the elytra, but replenish it directly from the rear.

#7. Beetles <aquatic, posture for replenishing air supply>/

1. regularly posing tail first at the water surface to replenish air/

2. regularly posing head first at the water surface to replenish air/

3. not noticeably posing regularly at the water surface to replenish air/

#8. Beetles <aquatic, how air is collected>/

1. collecting air at the water surface by exserting the tip of the abdomen through the surface film/

2. collecting air at the water surface by exserting one antenna to achieve a continuum of air with the ventral plastron/

3. replenishing air in the ventral plastron by exserting both antennae at the water surface/

4. incorporating bubbles of oxygen directly into the <ventral> plastron/

‘Plastron’: in the present context, a pile of fine hydrofuge hairs on the ventral surface of many aquatic beetles, in which air is collected and stored to supply oxygen for respiration when they are submerged. Air transferred from the plastron to the water-tight space under the elytra is respired via the terminal pair of abdominal spiracles. The plastron, which is often conspicuous as a bubble on the underside of the submerged insect, is a characteristic feature of hydrophilid beetles, and distinguishes them from dytiscids. The latter also store air under the elytra, but replenish it directly from the rear.

#9. Beetles <head-to-tail body length>/

mm long/

Length measured in normal posture (e.g., without tilting up the head).

#10. Body length/maximum body width/

#11. Elytral length/pronotal length <ratio>/

‘Pronotum’: the single, dorsal sclerite of the ‘prothorax’; the latter being the major part of the beetle’s thorax which is visible from above.

#12. Base of prothorax <whether much narrower than elytral bases>/

1. not or scarcely narrower than the combined elytral bases/

2. distinctly narrower than the combined elytral bases/

‘Prothorax’: the first (anterior) segment of the (three-segmented) thorax. In beetles this is usually relatively large, forming with the head a conspicuous, independently movable ‘fore-body’. It is composed of a single dorso-lateral sclerite, ‘the pronotum’, a ventral ‘prosternum’, and lateral ‘proepisterna’, and bears the front pair of legs.

‘Mesothorax’ and (larger) ‘Metathorax’: the second and third thoracic segments. These are fused together, constituting the ‘pterothorax’, which bears the elytra, (hind-)wings and mid- and hind-legs.

‘Notopleural suture’: a groove in the side of the prothorax (q.v.), separating the prosternum (q.v.) from the pronotum (q.v.). .

#13. Greatest prothoracic width <whether much narrower than greatest elytral width>/

1. not narrower or only slightly narrower than the greatest elytral width/

2. distinctly narrower than greatest elytral width/

‘Prothorax’: the first (anterior) segment of the (three-segmented) thorax. In beetles this is usually relatively large, forming with the head a conspicuous, independently movable ‘fore-body’. It is composed of a single dorso-lateral sclerite, ‘the pronotum’, a ventral ‘prosternum’, and lateral ‘proepisterna’, and bears the front pair of legs.

‘Mesothorax’ and (larger) ‘Metathorax’: the second and third thoracic segments. These are fused together, constituting the ‘pterothorax’, which bears the elytra, (hind-)wings and mid- and hind-legs.

‘Notopleural suture’: a groove in the side of the prothorax (q.v.), separating the prosternum (q.v.) from the pronotum (q.v.).

#14. <Elongate> body <whether widest immediately behind the thorax, or distally>/

1. noticeably widest immediately behind the thorax/

2. noticeably widest at the rear/

3. not noticeably widest either behind the thorax, or at the rear/

#15. Beetles <body shape, viewed from above>/

1. <more or less> round/

2. oval/

3. elongate-oval/

4. elongate/

5. slender/

It is safest, and still potentially useful, to bracket the possibilities by entering two or more states of this rather subjective character.

#16. Beetles <rotundity>/

1. only about 2 to 2.5 times as long as the maximum depth in lateral view: globular, less elongate and the elytra more rounded laterally than is usual in Hydroporus etc. /

2. about 2.5 to 3 times as long as the maximum depth in lateral view: not globular, somewhat elongate, the elytra not much rounded laterally/

#17. Beetles <presence of paired pronotal and elytral shining hairy bumps>/

1. characterised by two shining, hairy bumps (tubercles) towards the posterior of the pronotum, and a matching pair behind them on the shoulders of the elytra <Macronychus>/

2. without the pairs of pronotal and elytral shining, hairy bumps characteristic of Macronychus (q.v.) /

#18. Beetles <overall body shape: flattened, convex or cylindric>/

1. dorsally flattened/

2. dorsally somewhat convex/

3. dorsally strongly convex/

4. <more or less> cylindric/

#19. Beetles <convexity of undersides>/

1. convex beneath/

2. flat beneath/

#20. Beetles <asymmetric humping>/

1. asymmetrically humped, and tapered to the rear <Rhipiphoridae>/

2. not asymmetrically humped and tapered /

#21. Beetles <whether the closed elytra are drawn out to form a small point at their rear>/

1. with the closed elytra drawn out to form a very small but distinct point at the rear <Hydrovatus>/

2. with the closed elytra not drawn out to form small point at the rear/

#22. Beetles <presence of ventral cavities>/

1. having ventral body cavities into which the legs fold to conform with the general body surface/

2. without ventral body cavities for reception of the legs/

#23. Beetles <whether necked>/

1. conspicuously necked <distinctly narrowed between head and thorax>/

2. not necked/

#24. Beetles <whether waisted>/

1. not waisted <parallel-sided, or rounded>/

2. somewhat waisted/

3. conspicuously waisted/

#25. Beetles <long- or short-legged>/

1. conspicuously long-legged/

2. neither particularly long- nor short-legged/

3. decidedly short-legged/

#26. All the legs <whether very long>/

1. at least as long as the entire beetle <Macronychus>/

2. long, but none longer than the entire beetle /

#27. Beetles <colour>/

#28. Beetles <brightly coloured or marked>/

1. exhibiting bright ‘warning colours’/

2. without ‘warning colouration’ /

#29. Beetles <unicolorous, colour>/

1. entirely unicolorous yellow/

2. not entirely unicolorous yellow/

#30. Beetles <yellow and black Hydroporinae: marking>/

1. predominantly black with yellow markings/

2. predominantly yellow with black markings/

#31. Beetles <stripes or spots>/

1. with sharply defined elytral spots and/or blotches/

2. with elytral longitudinal stripes/

3. without sharply defined stripes, spots or blotches/

#32. Beetles <luminescence>/

1. luminescent from distal abdominal sternites/

2. not luminescent/

#33. Upper surfaces of body <vestiture>/

1. glabrous or subglabrous/

2. non-glabrous <clothed with distinct hairs, setae or scales>/

#34. Beetles <nature of hairines>/

1. with very short, appressed pubescence throughout/

2. with more or less raised pubsescence/

#35. Upper surfaces of body <vestiture, whether including stiff, erect bristles>/

1. exhibiting stiff, erect, dark bristles/

2. not bristly <without stiff, erect, dark bristles>/

#36. Upper surfaces of body <vestiture, whether including scales or scale-like setae>/

1. exhibiting scales or scale-like setae/

2. with neither scales nor scale-like setae/

#37. Beetles <whether conglobulating>/

1. rolling into a ball <conglobulating> when alarmed/

2. not conglobulating /

#38. Beetles <whether ‘clicking’>/

1. clicking and ‘jumping’ to right themselves when inverted/

2. not clicking and ‘jumping’ /

#39. Beetles <presence of rostrum: see Notes>/

1. equipped with a rostrum/

2. without a rostrum /

‘Rostrum’: a marked, rigid elongation of the front of the head (frons and vertex), on which the antennae are carried forward and which bears the (biting/chewing) mouthparts at its tip. This modification, characteristic of the curculionid families (weevils), is utilized by the females to bore holes in plant material (leaves, stems, fruits, bark, etc.) in which the eggs are deposited; but details of its significance for males and in relation to the adults’ feeding habits are elusive. The second character image provides a detailed comparison with a non-rostrate form.

#40. Beetles <whether prognathous>/

1. prognathous/

2. not prognathous/

‘Prognathous’ (in this context): having the mandibles projecting and clearly visible when the beetle is viewed from above.

#41. The head <of the beetle, whether visible from above>/

1. covered by the thorax <i.e., when the beetle is viewed from above>/

2. not covered by the thorax /

#42. Inclination of the head <from occipital foramen to mouth cavity, inclination from the longitudinal axis of the body in the living beetle>/

1. slight <at an angle of less than 45 degrees from the longitudinal axis of the beetle’s body>/

2. strong <at 45 to 90 degrees from the longitudinal axis of the beetle’s body>/

3. very strong <more than 90 degrees from the longitudinal axis of the beetle’s body>/

#43. Eyes <compound, presence>/

1. present /

2. absent/

#44. Eyes <compound, apparent number>/

1. two /

2. ostensibly four <the oft-encounterd partial division into an upper and lower eye being complete>/

#45. Eyes <whether strongly protuberant>/

1. strongly protuberant/

2. not strongly protuberant/

#46. Eyes <of Dytiscidae in frontal view: indentation of the front edge>/

1. vertically straight edged at the front/

2. with the front edge conspicuously indented above the antennal insertions/

#47. Eyes <pubescent or not>/

1. bristly <with interfacetal setae>/

2. without <interfacetal> bristles/

#48. Eyes <finely or coarsely facetted>/

1. finely facetted/

2. coarsely facetted/

#49. Ocelli <presence>/

1. present/

2. absent/

‘Ocelli’: simple eyes, additional to and located between or behind the compound eyes.

#50. Ocelli <when present, number>/

1. solitary/

2. paired/

‘Ocelli’: simple eyes, additional to and located between or behind the compound eyes.

#51. The frons <whether transversely ridged>/

1. with a transverse ridge between the eyes/

2. without a transverse ridge between the eyes/

#52. The labrum <upper lip, whether externally detectable>/

1. externally visible from above/

2. not externally apparent/

#53. Mandibles <presence>/

1. present <implicit>/

2. absent or vestigial/

#54. Mandibles <presence of mola>/

1. with a well developed mola/

2. with a reduced mola/

3. without a mola/

#55. Mandibles <prosthecae, presence and degree of development>/

1. with well developed prosthecae/

2. with reduced prosthecae/

3. without prosthecae/

#56. The mandibular apices <teeth or lobes>/

1. simple <without teeth or lobes, truncate or rounded>/

2. bidentate or bilobed/

3. multidentate or multilobed/

#57. The incisor edges of the mandibles <teeth>/

1. simple/

2. with a single tooth/

3. with two or more teeth/

#58. The maxillae <apical structures, additional to the palp>/

1. with distinct galea and lacinia apically to the palp/

2. with a single apical structure additional to the palp/

3. comprising the palp, without conspicuous apical lobes/

#59. The maxillae <presence of galea>/

1. with an outer palpiform lobe (the galea) additional to the 4-segmented maxillary palp/

2. without a conspicuous galea <implicit>/

The maxillae and their palps are borne under (posteriorly to) the mandibles, between the upper (labrum) and lower (labium) lips. The (1-)4(-7)-segmented maxillary palps are to be distinguished from the (1-)2(-4)-segmented labial palps, which are located posteriorly to them.

#60. The maxillae <whether with stylet-like lobes>/

1. with stylet-like lobes/

2. without stylet-like lobes <implicit>/

#61. The maxillary palps <whether normal>/

1. normal, flexible/

2. if visible, short and rigid/

#62. The maxillary palps <whether much shorter than the antennae>/

1. scarcely visible, being very much shorter than the antennae/

2. relatively conspicuous /

#63. The maxillary palps <elongation>/

1. conspicuously elongated, sometimes longer than the antennae/

2. not especially elongated /

#64. The maxillary palps <whether less than twice as long as the antennae>/

1. less than twice as long as the antennae/

2. about twice as long as the antennae/

#65. The maxillary palps <elongation>/

1. conspicuously elongated, sometimes longer than the antennae/

2. not especially elongated /

#66. The apical segment of the maxillary palps <shape>/

1. cylindrical to fusiform/

2. somewhat expanded and truncate to subtriangular/

3. securiform to cultriform <axe- to knife-shaped>/

4. aciculate/

#67. The apical segment of the maxillary palps <relative length>/

1. shorter than the penultimate one/

2. longer than the penultimate one/

#68. The apical segment of the labial palps <shape>/

1. more or less expanded apically/

2. not expanded apically <cylindrical to fusiform>/

#69. Antennae <length relative to length of insect>/

1. very short <less than a fifth of the insect’s head to tail length; antenna/insect length = 0.1–0.2>/

2. short <less than half of the insect’s head to tail length; antenna/insect length = 0.2–0.4>/

3. about half the insect's head to tail length <antenna/insect length = 0.4–0.6>/

4. long, but not exceeding the insect’s head to tail length <more than half the insect's length; antenna/insect length = 0.6–1.0>/

5. longer than the insect's head to tail length <antenna/insect length = 1.0+>/

Antennae of beetles nearly always have more than three segments (usually 7–11). The palps, with which they might otherwise be may be confused, usually have (1-)3 segments (labial palps) or (2-)4(-5) segments (maxillary palps).

#70. Antennae <insertion>/

1. inserted on the front of the head, with the distance between their bases no greater than the length of their first segment/

2. inserted further apart than the length of their first segment /

#71. Antennae <whether strongly asymmetric>/

1. strongly asymmetric/

2. not strongly asymmetric <including merely ‘elbowed’ or ‘bent’>/

#72. Antennae <whether elbowed>/

1. conspicuously elbowed <bent>/

2. not elbowed /

#73. Antennae <number of segments>/

segmented/

#74. Antennae <whether hairy>/

1. hairy/

2. not hairy/

#75. Antennae <of beetles, presence of scape>/

1. with the scape much-elongated <a single, elongated basal segment>/

2. without a much-elongated scape /

#76. Antennal scape <whether swollen>/

1. swollen/

2. not swollen /

#77. Antennae <shape>/

1. filiform <including moniliform>/

2. gradually expanding towards the apex/

3. clubbed/

4. serrate/

5. pectinate/

#78. Antennal clubs <whether lamellate (laminate)>/

1. lamellate <laminate>/

2. not lamellate /

#79. Antennal clubs <number of segments>/

segmented/

#80. Antennal clubs <detailed construction>/

1. spherical, comprising two small basal segments and a large terminal one <Cerylonidae>/

2. not comprising two small basal segments and a large terminal one /

#81. Antennal clubs <whether preceded by a cupular segment>/

1. preceded by a cupule/

2. without a cupule /

#82. Antennal segment 8 <length relative to the second>/

1. shorter than the second/

2. at least as long as the second/

#83. Antennal segment 8 <within the club, whether smaller than 7 and 9>/

1. <markedly> smaller than segments 7 and 9 <Leiodidae>/

2. not <markedly> smaller than 7 and 9 /

#84. Antennal insertions <whether visible from above>/

1. visible from above/

2. hidden from above/

#85. Antennal insertions <whether covered by extensions from the frons>/

1. hidden by lateral extensions of the frons <Tenebrionidae>/

2. not hidden by lateral extensions of the frons/

‘Frons’ (of insects): the upper front part of the head.

Antennae of beetles nearly always have more than three segments (usually 7–11). The palps, with which they might be might otherwise be confused, usually have (1-)3 segments (labial palps) or (2-)4(-5) segments (maxillary palps).

#86. Antennal insertions <whether located in fossae>/

1. ‘countersunk’ within saucer-like fossae/

2. not in fossae <flush or raised>/

#87. Prothorax <length relative to width>/

1. shorter than wide/

2. about as long as wide/

3. longer than wide/

‘Prothorax’: the first (anterior) segment of the (three-segmented) thorax. In beetles this is usually relatively large, forming with the head a conspicuous, independently movable ‘fore-body’. It is composed of a single dorso-lateral sclerite, ‘the pronotum’, a ventral ‘prosternum’, and lateral ‘proepisterna’, and bears the front pair of legs.

‘Mesothorax’ and (larger) ‘Metathorax’: the second and third thoracic segments. These are fused together, constituting the ‘pterothorax’, which bears the elytra, (hind-)wings and mid- and hind-legs.

‘Notopleural suture’: a groove in the side of the prothorax (q.v.), separating the prosternum (q.v.) from the pronotum (q.v.).

#88. Prothorax <of elongate beetle> at its widest <width relative that of the to abdomen>/

1. markedly narrower than the adjoining part of the abdomen/

2. not markedly narrower than the adjoining part of the abdomen/

#89. Prothorax <presence of a suture between pronotum and propleuron>/

1. with notopleural sutures/

2. without notopleural sutures/

#90. Pronotal length/maximum pronotal width <ratio>/

#91. The pronotum <shape>/

1. narrowing <at least somewhat> towards the rear/

2. not narrowing towards the rear/

#92. The pronotum <longitudinal furrows>/

1. with five full length, longitudinal furrows/

2. without five full length longitudinal furrows <ignore pits>/

#93. The pronotum <with or without two sharply defined ridges>/

1. with two sharply defined longitudinal ridges/

2. without sharply defined ridges/

#94. The <pair of> longitudinal <pronotal> ridges <whether incurving posteriorly>/

1. sharply incurving posteriorly, almost meeting adjacent to the scutellum /

2. remaining well separated throughout their length/

#95. The pronotum <presence of large pits>/

1. with large pits/

2. without large pits/

#96. The pronotum <paired longitudinal furrows adjoining a pair on the elytra>/

1. with a single longitudinal furrow posteriorly on each side, these located two-thirds of the way from the mid-line and adjoining a pair of short furrows at the bases of the (closed) elytra/

2. without the pair of longitudinal furrows characteristic of Hydroglyphus, Bidessus et al. (q.v.)/

#97. The pronotum <presence of a single, short median-longitudinal furrow towards the outer margin on each side>/

1. with a single, short median-longitudinal furrow towards the outer margin on each side/

2. without a single, short median-longitudinal furrow towards the outer margin on each side/

#98. The pronotum <shortly furrowed on each side>/

1. with a pair of short longitudinal furrows, one on each side <some Hydroporinae>/

2. without a short longitudinal furrow on each side/

#99. The pronotum <uniform or patterned>/

1. patterned <more or less conspicuously>/

2. not conspicuously patterned <uniform>/

#100. The <uniform> pronotum <colour>/

1. uniformly pale/

2. uniformly dark/

3. reddish/

4. mid-brown/

#101. The pronotum <colouring relative to the elytra>/

1. paler than the elytra/

2. coloured similarly to the elytra/

3. darker than the elytra/

#102. The pronotum <colour patterns: Dytiscidae>/

1. pale with a broad black crescent at the rear/

2. with two black bars across the middle enclosing a yellowish one/

3. pale with black bands on the front and hind margins (sometimes with a thin yellow line preceding the front band)/

4. dark, yellow margined either all round or at front and sides only/

5. pale, with a broad dark bat-shaped band across the middle/

#103. Scutellum <presence: Dytiscidae>/

1. present <visible at junction of pronotum with elytra>/

2. absent/

#104. Scutellum <relative length>/

1. much longer than broad /

2. not much longer than broad/

#105. The scutellum <elevation>/

1. elevated <abruptly and fairly sharply above the mesoscutum, in lateral view>/

2. not elevated/

#106. The pronotum and elytra <hairy covering>/

1. covered with fine hair /

2. hairless /

#107. The mesoventrite <mesosternum, whether keeled or with a posterior point>/

1. keeled/

2. not keeled, but with a dorsal point/

3. not keeled, and without a dorsal point/

#108. Metaventrite <metasternum, whether exhibiting a transverse groove>/

1. with a transverse groove/

2. without a transverse groove/

‘Metaventrite' (often but unsatisfactorily called the ‘metasternum’: the main ventral sclerite of the metathorax.

‘Sclerites’: the conspicuously hardened (scerotised) regions of the segments. Those of adjoining segments may be fused (disguising the segmentation), or separated by zones of membranous cuticle (in flexible parts of the body).

#109. The prosternal process <shape>/

1. arising in a different plane from the prosternum, resulting in a distinct ridge at its origin <“the neck of the prosternal process with a sharply raised edge defining a distinct step” (Foster & Friday)>/

2. arising in the same plane as the prosternum, without a distinct ridge at its origin <“not stepped”>/

#110. The prosternal process <shape>/

1. elongate-oval, glabrous and slightly domed/

2. broad, flat and hairy/

3. narrow and spear-shaped, with a median longitudinal ridge crested with curved hairs/

#111. Mid-and hind-legs <whether much modified>/

1. oar-like and much shorter than the fore-legs, which are elongated and modified for grasping prey <Gyrinidae>/

2. not as in Gyrinidae (q.v.) /

#112. The front tibia <shape>/

1. very conspicuously asymmetrically expanded and emarginate near the attachment of the tarsus <Megasternum>/

2. more or less club-shaped, not or scarcely emarginate near the attachment of the tarsus/

#113. The fore-leg coxal cavites <closed or open behind>/

1. closed behind/

2. open behind/

The beetle leg exhibits six primary segments, viz., coxa, trochanter, femur, tarsus, and the terminal ‘pretarsus’.

1. ‘Coxa’: the short first segment, which usually articulates proximally with the abdomen, and distally with the trochanter.

(‘Coxal cavity’: a cavity in the thorax into which the coxa fits.)

2. ‘Trochanter’: the short second segment, between coxa and femur, which in beetles freely articulates with the former but is firmly attached to the latter.

3. ‘Femur’: the third leg segment, articulating distally with the tibia. This is usually the stoutest and strongest segment, and is sometimes the longest. It sometimes bears long spines, but never exhibits movable spurs, and is enlarged in the hind legs of species that jump.

4. ‘Tibia’: the fourth leg segment, articulating distally with the tarsus. Tibiae are usually expanded towards their apices, which bear combs of spines, two of which are enlarged, articulated, and known as ‘spurs’. The fore tibiae are often expanded and toothed on the outer side, associated with digging.

5. ‘Tarsus’: the fifth primary segment of the beetle leg, which articulates proximally with the tibia, and distally with the pretarsus, and is usually itself resolvable into (2-)4–5 movable segments (‘tarsomeres’).

6. ‘Pretarsus’: the terminal leg component, which usually comprises paired ‘claws’ and the median ‘empodium’.

#114. The fore-leg coxal cavities <extent of closure>/

1. broadly open/

2. narrowly open/

3. narrowly closed/

4. broadly closed/

#115. The fore-leg coxal cavities <separation>/

1. medianly confluent <contiguous>/

2. narrowly separated/

3. quite widely separated/

#118. The fore-leg coxal cavities <whether closed or open internally>/

1. internally open/

2. internally closed by a slender bar/

3. broadly closed internally/

#119. Hind coxae <of beetles, whether movable. Applicable, with caution, only to living specimens>/

1. movable /

2. immovably fixed to the metasternum and dividing the first abdominal sternite/

This character appears to be taxonomically meaningful, but apparently cannot be applied reliably for identifying dead specimens.

The beetle leg exhibits six primary segments, viz., coxa, trochanter, femur, tarsus, and the terminal ‘pretarsus’.

1. ‘Coxa’: the short first segment, which usually articulates proximally with the abdomen, and distally with the trochanter.

(‘Coxal cavity’: a cavity in the thorax into which the coxa fits.)

2. ‘Trochanter’: the short second segment, between coxa and femur, which in beetles freely articulates with the former but is firmly attached to the latter.

3. ‘Femur’: the third leg segment, articulating distally with the tibia. This is usually the stoutest and strongest segment, and is sometimes the longest. It sometimes bears long spines, but never exhibits movable spurs, and is enlarged in the hind legs of species that jump.

4. ‘Tibia’: the fourth leg segment, articulating distally with the tarsus. Tibiae are usually expanded towards their apices, which bear combs of spines, two of which are enlarged, articulated, and known as ‘spurs’. The fore tibiae are often expanded and toothed on the outer side, associated with digging.

5. ‘Tarsus’: the fifth primary segment of the beetle leg, which articulates proximally with the tibia, and distally with the pretarsus, and is usually itself resolvable into (2-)4–5 movable segments (‘tarsomeres’).

6. ‘Pretarsus’: the terminal leg component, which usually comprises paired ‘claws’ and the median ‘empodium’.

#120. Hind coxae <lateral extension>/

1. much expanded and extended laterally to meet the elytra/

2. not extended laterally to meet the elytra /

#121. Hind coxae <whether posteriorly shaped to receive the femur>/

1. posteriorly shaped <e.g., declinate or concave> to receive the retracted femur/

2. not shaped posteriorly to receive the femur /

#122. The hind coxae <whether produced and plate-like behind>/

1. much enlarged and produced behind into large flat plates which partly conceal the hind femora/

2. not produced behind into flat plates partly concealing the hind femora /

The beetle leg exhibits six primary segments, viz., coxa, trochanter, femur, tarsus, and the terminal ‘pretarsus’.

1. ‘Coxa’: the short first segment, which usually articulates proximally with the abdomen, and distally with the trochanter.

(‘Coxal cavity’: a cavity in the thorax into which the coxa fits.)

2. ‘Trochanter’: the short second segment, between coxa and femur, which in beetles freely articulates with the former but is firmly attached to the latter.

3. ‘Femur’: the third leg segment, articulating distally with the tibia. This is usually the stoutest and strongest segment, and is sometimes the longest. It sometimes bears long spines, but never exhibits movable spurs, and is enlarged in the hind legs of species that jump.

4. ‘Tibia’: the fourth leg segment, articulating distally with the tarsus. Tibiae are usually expanded towards their apices, which bear combs of spines, two of which are enlarged, articulated, and known as ‘spurs’. The fore tibiae are often expanded and toothed on the outer side, associated with digging.

5. ‘Tarsus’: the fifth primary segment of the beetle leg, which articulates proximally with the tibia, and distally with the pretarsus, and is usually itself resolvable into (2-)4–5 movable segments (‘tarsomeres’).

6. ‘Pretarsus’: the terminal leg component, which usually comprises paired ‘claws’ and the median ‘empodium’.

#123. The hind coxal plates <shape>/

1. smoothly rounded posteriorly, and leaving the last three abdominal sternites freely visible/

2. each with a point on the posterior margin, and covering part of the sixth abdominal sternite/

#124. Hind coxae <whether steeply, transversely declined>/

1. with a steep transverse declivity against which the femur retracts/

2. without the steep transverse declivity characteristic of Dryopoidea/

#125. The inner parts (‘processes’) of the hind coxae <whether contributing to a flat longitudinal keel>/

1. constituting longitudinal plates that are fused to one another and joined with the metasternum, endowing the beetle ventrally with a flat, median longitudinal keel/

2. not incorporated with the metasternum in a flat, median longitudinal keel /

#126. The hind coxal <median> processes <relative width>/

1. very broad, taken together at least as wide as long and forming a distinctive plate with a W-shaped hind margin (see illustrations) /

2. longer than broad, the hind margin not W-shaped <pointed, straight or wavy (see illustrations)>/

#127. The hind femora <enlargement>/

1. enlarged for hopping/

2. not especially enlarged/

#128. The undersides of the hind femora <bristles>/

1. each with a short comb of bristles (sometimes only three) at the outer rear corner/

2. without bristles at their outer rear corners, or the bristles weak and not forming a comb/

#129. Hind tibia <of Dytiscidae, form>/

1. longer than wide, and longer than the relatively slender spurs/

2. scarcely longer than wide, with one spur massive relative to the other and both as long as the body of the tibia/

#130. The hind claws <of Dytiscidae, paired or single>/

1. paired/

2. single/

#131. The <paired> hind tarsal claws <whether equal>/

1. more or less equal in length/

2. very unequal in length/

#132. Tarsal segmentation formula <fore-, mid-, hind-leg: ostensible segmentation, ignoring any small cylindrical segments obscured by lobes on those preceding them>/

1. 0, 5, 5/

2. 5, 5, 5/

3. 5, 5, 4/

4. 4, 4, 4/

5. 4, 4, 3/

6. 3, 4, 4/

7. 3, 3, 3/

8. 5, 4, 4/

9. 4, 4, 5/

10. 5, 3, 3/

11. 4, 3, 3/

12. 0–2, 3, 3/

#133. <Presence of tarsi with bilobed segments>/

1. some of the tarsi exhibiting <one or more> conspicuously bilobed segments/

2. none of the tarsi with conspicuously bilobed segments/

#134. <Presence and location of hidden tarsal segments>/

1. some tarsi with a tiny penultimate segment hidden by distal lobing of the fourth and fused to the fifth/

2. some of the tarsi with a tiny basal segment that is hard to detect/

3. none of the tarsi with ‘hidden’ segments/

#135. The front tarsi <reduction>/

1. present and well developed /

2. reduced or absent/

#136. The front tarsi <number of segments, relative to mid-tarsi>/

1. with <at least> as many segments as the mid-tarsi/

2. with one segment fewer than the mid-tarsi/

#137. The front tarsi <number of segments, including any ‘hidden’ segments>/

1. 3-segmented/

2. 4-segmented/

3. 5-segmented/

#138. The front tarsi <conspicuous modification>/

1. each having the three proximal segments expanded and approximated to form a conspicuous rounded disc/

2. not each exhibiting a conspicuous, expanded rounded disc <implicit>/

#139. The apical segment <of the front tarsi: relative length>/

1. longer than the rest together/

2. about as long as the rest together/

3. shorter than the rest together/

#140. Mid-leg tarsi <total number of segments, including any ‘hidden’ segments>/

1. 3-segmented/

2. 4-segmented/

3. 5-segmented/

#141. Mid-leg tarsi <readily visible versus ‘hidden’ segments>/

1. pentamerous <with 5 segments, all conspicuous>/

2. pseudotetramerous <with 4 obvious segments, plus a reduced one>/

3. tetramerous <with 4 segments, all easily seen>/

4. pseudotrimeous <with 3 obvious segments plus a reduced penultimate one>/

5. trimerous <with 3 segments, all easily seen>/

6. with fewer than three segments/

#142. The claws of the mid-leg tarsi <whether appendaged>/

1. with an appendage <on each>/

2. not appendaged/

#143. The appendages <of the claws of the mid-leg tarsi, type>/

1. not or only lightly sclerotized <usually pubescent>/

2. heavily sclerotized, blade-like/

3. heavily sclerotized, spine-like or bristle-like/

#144. The claws of the mid-leg tarsi <whether simple or ornamented>/

1. simple/

2. one-toothed or bifid/

3. serrate, denticulate or pectinate/

#145. The claws of the mid-leg tarsi <whether associated with an empodium>/

1. with an empodium between them <with or without bristles>/

2. without an associated empodium/

#146. Hind tarsi <number of segments, relative to mid-tarsi>/

1. with at least as many segments as the mid-tarsi/

2. with one segment fewer than the mid-tarsi/

#147. Hind tarsi <number of segments, including any ‘hidden’ segments>/

1. 3-segmented/

2. 4-segmented/

3. 5-segmented/

#148. Hind tarsi <of beetles, whether modified for swimming>/

1. flattened oar-like for swimming/

2. not flattened oar-like /

#149. Hind tarsi <presence of swimming hairs>/

1. equipped with ‘swimming hairs’ <sometimes requiring careful observation>/

2. without ‘swimming’ hairs /

#150. The first segment of the hind tarsi <relative length>/

1. longer than the rest of the tarsus/

2. shorter than the rest of the tarsus/

#151. Hind tarsi <relative length of second segment>/

1. with the second segment longest/

2. with the apical segment longer than the second/

3. with the apical and second segments about equal in length/

#152. Hind tarsi <relative lengths of apical and second segments>/

1. with the apical segment only about half as long as the second/

2. with the apical segment about three-quarters the length of the second/

3. with the second and apical segments almost equal in length/

#153. Hind tarsi <length of apical segment relative to all the rest>/

1. with the apical segment about equal to segments 3+4, with segment 2 very short/

2. with the apical segment longer than segments 3+4, and segment 2 not very short but not longer than 3+4/

3. with the apical segment at least as long as all the rest together/

#154. Swimming hairs <general location>/

1. confined to the hind legs/

2. on both middle and hind legs/

#155. Swimming hairs <when present, presence on tibiae>/

1. confined to the tarsi/

2. present on both tibiae and tarsi/

#156. <Adult> elytra <presence>/

1. present /

2. absent/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#157. Elytral length/maximum width across the elytra <i.e., with the elytra closed>/

Measurements made in the resting position, with the elytra closed. The length of the elytra is measured from the base of the scutellum (or mid-posterior edge of the pronotum if the scutellum is concealed) to the conjoined elytral apices or to an imaginary line joining the separated elytral apices. The ‘elytral width’ is the greatest combined width or, when the elytra are widely separated their tips, the length of the longest line joining their two outside edges.

#158. Elytra <whether unusually elongate and tapered>/

1. individually distinctly tapered to their apices <markedly posteriorly separated when closed>/

2. not individually tapered /

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#159. Elytra <when closed, whether meeting on the mid-line>/

1. meeting along the length of the mid-line /

2. not meeting along the full length of the mid-line/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#160. Elytra <when closed, length relative to abdomen>/

1. covering most to all of the abdomen /

2. short, exposing several <(2-)3–6> terminal abdominal tergites/

3. greatly reduced <vestigial>/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

‘Abdominal tergite’: the sclerotised dorsal region (‘sclerite’, q.v.) of a visible body segment. Of the abdomen, usually equivalent to ‘segment’.

‘Abdominal ventrite’: the sclerotised ventral region (‘sclerite’, q.v.) of a visible abdominal segment. The number of ventrites is often fewer than the number of true segments.

‘Abdominal sternite’: the sclerotised ventral region (‘sclerite’, q.v.) of an abdominal segment, whether visible or not. The number of sternites corresponds with the number of segments.

#161. Elytra <when closed> exposing <number of abdominal tergites>/

1. no more than part of the terminal tergite <usually the pygidium>/

2. at least one but fewer than three complete abdominal tergites/

3. at least three complete abdominal tergites/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

‘Abdominal tergite’: the sclerotised dorsal region (‘sclerite’, q.v.) of a visible body segment. Of the abdomen, usually equivalent to ‘segment’.

‘Pygidium’: the terminal (tail-end) exposed and sclerotised abdominal tergite. It may be either tergite 7 or 8.

#162. The pygidium <exposure>/

1. at least partly exposed beyond the long elytra/

2. entirely concealed by the ends of the elytra even when viewed from behind/

‘Pygidium’: the last (i.e., the eighth) visible abdominal tergite in Coleoptera. This character seems to provide the only absolute distinction between Aphodiidae and assorted other Scarabaeidae sensu lato. Cf. Britton (1970).

#163. Elytra <whether truncate>/

1. truncate/

2. not truncate/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#164. Elytra <subquadrate or elongate>/

1. subquadrate/

2. elongate/

#165. Elytra <shape detail>/

1. broadest near the base/

2. broadest near the middle/

3. broadest posteriorly/

#166. Elytra <hard or soft>/

1. hard/

2. soft/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#167. Elytra <glossy or dull>/

1. glossy/

2. dull/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#168. Elytra <iridescent or not>/

1. iridescent/

2. not iridescent /

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#169. Elytra <whether smooth>/

1. rough/

2. tuberculate/

3. spiny/

4. ribbed <ridged>/

5. smooth/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#170. Elytra <longitudinal ribs (ridges)>/

1. with conspicuous longitudinal ribs <ridges; exclusive of the sutural margin>/

2. not conspicuously longitudinally ribbed/

#171. Elytra <when ribbed, number of ribs on each>/

ribbed/

#172. Elytra <presence of a small tooth near the tip>/

1. with a very small tooth projecting from the costa near the tip <Nebrioporus spp.>/

2. without the small tooth near the tip that characterises Nebrioporus spp. /

#173. Elytra <colouring and marking: smaller Dytiscidae>/

1. mottled yellow and black <at x 10 magnification>/

2. dark with yellow spots or bands/

3. dark with full length, wide pale margins/

4. uniformly reddish or mid-brown, no more than faintly streaked or spotted/

5. uniformly very dark or black, no more than faintly streaked or spotted/

6. yellow, each with 5–6 coalescing black stripes/

#174. Elytra <pattern of pale markings: Graptodytes/Stictonectes>/

1. black with transverse, pale, complexly wavy markings only/

2. black, with one or more pale longitudinal stripes running from the pronotum to near the tip (without the transverse wavy markings characteristic of Stictonectes)/

#175. Elytra <striping>/

1. longitudinally with distinct dark stripes/

2. indistictly dark striped longitudinally/

3. not dark-striped/

#176. Elytra <presence of striae, exclusive of sutural striae>/

1. longitudinally striate/

2. without longitudinal striae <discounting sutural striae and rows of punctures>/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

‘Stria’: an impressed line. ‘Striate’: furnished with striae.

#177. Elytra <presence of striae or rows of punctures: ‘Sphaeridiidae’>/

1. with sutural striae only/

2. striate or with regular rows of punctures/

‘Stria’: an impressed line. ‘Striate’: furnished with striae.

#178. Elytra <transverse striation>/

1. predominantly finely but rather conspicuously transversely striated <transversely sculptured> across lines of punctured striae/

2. not predominantly transversely striated across lines of puntured striae /

‘Stria’: an impressed line. ‘Striate’: furnished with striae.

#179. The middle part of the elytra <small and large punctures>/

1. with approximately equal numbers of small and large punctures scattered in the visibly reticulate surface/

2. with scattered punctures all more or less of the same size, or sometimes also with lines of larger ones/

#180. Elytra (and pronotum) <punctures and pits>/

1. with numerous small punctures, and pits 4–5 times their diameter scattered among them/

2. finely punctured, the numerous punctures all about the same size/

#181. Elytra <distictive sculpture>/

1. reddish and elongate, distinctively sculptured with numerous, short longitudinal cuts in the reticulated surface <Liopterus>/

2. not sculptured with numerous, short longitudinal cuts in a reticulated surface <not as in Liopterus>/

#182. Elytra <presence of strong ridges reaching only halfway>/

1. each exhibiting a pair of strong longitudinal ridges, with one extending only halfway from the shoulder <Stenelmis>/

2. lacking the pattern of longitudinal ridges characteristic of Stenelmis (q.v.) /

#183. Elytra <longitudinal ridges>/

1. each with a single, strong, median-longitudinal ridge/

2. not exhibiting a single, strong, median-longitudinal ridge /

#184. Elytra <presence of sutural striae>/

1. each with a well marked sutural stria <full length or not, adjoining the suture (q.v.)>/

2. without well marked sutural striae/

#185. The sutural striae <relative length>/

1. extending almost the full length of the suture <Hydroglyphus>/

2. extending no more than two-thirds towards the rear <Bidessus>/

‘The suture’: in Coleoptera, used to denote the line of junction between the elytra when the latter are closed over the beetle’s back.

#186. The rear halves of the elytra <grooving near the mid-line>/

1. each with a distinct groove <elytral suture, sutural stria> alongside the rear of the midline/

2. without a groove alongside the midline/

#187. Scutellary striole <of elytra, presence>/

1. present/

2. absent/

‘Scutellary striole’: a short stria (q.v.) or row of punctures situated laterally to the scutellum and not extending far posteriorly.

#188. Elytra <vestiture - glabrous or not>/

1. non-glabrous <i.e., with hairs, bristles or scales>/

2. glabrous/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#189. Elytra <presence of epipleura>/

1. with epipleura/

2. without epipleura/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

‘Epipleuron’: an infolding or incurving of the costa of the elytron (i.e., its leading edge, when the elytra are opened), which usually fits against the sides of the abdomen when the elytra are closed.

#190. The elytral epipleura <extent>/

1. reaching to the tips of the elytra/

2. falling short of the elytral tips/

‘Elytra’: paired organs representing the mesothoracic wings, which when closed usually (but not always) meet along the median line, and constitute a hardened cover for the beetle's hind-wings and abdomen. They are usually held open in flight, allowing free movement of the hind-wings.

#191. The elytral epipleura <whether divided into two parts>/

1. divided into two parts by a distinct ridge at the outer corner of the elytron/

2. without a dividing ridge/

#192. Beetles <details of hairiness and microreticulation: Oreodytes, Scarodytes>/

1. dorsally microreticulate and hairless/

2. dorsally shiny and without microreticulation beneath the covering of hair/

Data and illustrations exclusively from Balfour-Browne, who clearly demonstrated the taxonomic potential of elytral surface microstructure. Sadly, in common with much taxonomic work from the turn of the 19th Century on, his account is long on phylogenetic speculation and short on properly recorded comparative data.

#193. Elytra <presence of microreticulation>/

1. microreticulate, with a fine impressed reticulum <this often less conspicuous in the disc than towards the apex>/

2. without a microreticulum/

#194. The <elytral> mictoreticulation <pattern>/

1. regular/

2. transverse/

3. longitudinal/

#195. <Hind, metathoracic> wings <presence>/

1. well developed <presumed propellant>/

2. absent or much reduced/

The metathoracic wings of beetles, when functional for flying, are usually longer than the elytra (q.v.), and are normally folded and stored beneath the elytra when the insect is not flying. Not uncommonly (especially island and montane forms), however, they are more or less atrophied.

#196. <Hind, metathoracic> wings <spiral rolling>/

1. with the apical part spirally rolled/

2. not apically rolled /

#197. <Hind, metathoracic> wings <absence of venation>/

1. veined /

2. without veins/

#198. <Hind, metathoracic> wings <fringing>/

1. fringed with long hairs on the hind margin/

2. not fringed /

#199. Abdominal tergites <number>/

‘Abdominal tergite’: the sclerotised dorsal region (‘sclerite’, q.v.) of a visible body segment. Usually, 8 tergites (representing 10 segments) can be counted on the upper surface of the abdomen: segment 9 is the much modified genital segment, which is hidden within the body, and segment 10 is greatly reduced. The visible tail-end tergite represents segment 8, and is called the ‘pygidium’.

‘Abdominal ventrite’: the sclerotised ventral region (‘sclerite’, q.v.) of a visible abdominal segment. The number of ventrites is often fewer than the number of true segments.

‘Abdominal sternite’: the sclerotised ventral region (‘sclerite’, q.v.) of an abdominal segment, whether visible or not. The number of sternites corresponds with the number of segments.

#200. The end of the abdomen <extension-pointed>/

1. extended as a long, narrow point beyond the ends of the truncate elytra/

2. not extended as a long, narrow point beyond the ends of the elytra /

#201. Exposed abdominal sternites <= ventrites: number>/

‘Abdominal tergite’: the sclerotised dorsal region (‘sclerite’, q.v.) of a visible body segment. Usually, 8 tergites (representing 10 segments) can be counted on the upper surface of the abdomen: segment 9 is the much modified genital segment, which is hidden within the body, and segment 10 is greatly reduced. The visible tail-end tergite represents segment 8, and is called the ‘pygidium’.

‘Abdominal ventrite’: the sclerotised ventral region (‘sclerite’, q.v.) of a visible abdominal segment. The number of ventrites is often fewer than the number of true segments.

‘Abdominal sternite’: the sclerotised ventral region (‘sclerite’, q.v.) of an abdominal segment, whether visible or not. The number of sternites corresponds with the number of segments.

#202. Exposed abdominal sternites <articulation>/

1. all articulated and movable/

2. comprising both fused and movable components/

3. all fused and immovable/

#203. Exposed abdominal sternites immovably joined <= ‘connate ventrites’: number>/

‘Abdominal tergite’: the sclerotised dorsal region (‘sclerite’, q.v.) of a visible body segment. Usually, 8 tergites (representing 10 segments) can be counted on the upper surface of the abdomen: segment 9 is the much modified genital segment, which is hidden within the body, and segment 10 is greatly reduced. The visible tail-end tergite represents segment 8, and is called the ‘pygidium’.

‘Abdominal ventrite’: the sclerotised ventral region (‘sclerite’, q.v.) of a visible abdominal segment. The number of ventrites is often fewer than the number of true segments.

‘Abdominal sternite’: the sclerotised ventral region (‘sclerite’, q.v.) of an abdominal segment, whether visible or not. The number of sternites corresponds with the number of segments.

#204. Abdominal segment 8 <with or without functional spiracles>/

1. with apparently functional spiracles/

2. apparently without functional spiracles/

#205. Adults <whether adults predacious>/

1. predacious <specify prey>/

2. not predacious/

#206. Adults <non-predacious adults, diet>/

1. necrophagous/

2. feeding on dried animal remains/

3. phytophagous <live plant material: specify kinds>/

4. consuming decaying plant material <other than wood>/

5. eating dried plant material or stored plant products/

6. boring into living wood/

7. consuming rotting wood/

8. boring into dead wood/

9. mycetophagous <specify>/

10. coprophagous/

11. parasitic <specify>/

It is hard to obtain unambiguous records of what non-carnivorous adult beetles actually consume and digest. In particular, those involved with rotting wood are probably often ‘mycetophagous’.

#207. Adults <non-aquatic adults, habitat>/

1. in living vegetation/

2. in decaying plant material/

3. in rotting wood/

4. in dried plant material/

5. under bark/

6. on lichens/

7. associated with fungi/

8. associated with dung/

9. associated with carrion/

10. on shed fur or feathers <in nests or burrows>/

11. associated with flowers/

12. under stones/

13. in stored plant products/

#208. <Habitats>/

#209. The larvae <general form>/

1. campodeiform/

2. eruciform/

3. scarabaeiform/

4. apodous/

#210. The larvae <outline shape, viewed from above>/

1. strongly flattened and disc-like/

2. neither strongly flattened nor disc-like <implicit>/

#211. The larvae <shape, viewed from above>/

1. elongate and more or less parallel-sided/

2. oblong to ovate <not parallel-sided>/

#212. The larvae <whether C-shaped in lateral view>/

1. C-shaped in lateral view <strongly curved ventrally>/

2. not C-shaped <more or less straight ventrally: implicit>/

#213. Vestiture <of the larva, nature>/

1. restricted to fine hairs or setae/

2. not restricted to fine hairs or setae <e.g., including bristles, scales, expanded or complex hairs>/

#214. The larvae <dorsal pigmentation>/

1. dorsally heavily pigmented or sclerotized/

2. only very lightly pigmented or sclerotized/

#215. The larvae <ventral pigmentation>/

1. more or less heavily pigmented/

2. only very lightly pigmented/

#216. The antennae <of the larva, number of segments>/

segmented/

#217. The antennae <of the larva, length relative to the width of the head>/

1. less than 0.15 x the <maximum> with of the head/

2. 0.15–0.5 x the head width/

3. more than 0.5 x the width of the head/

#218. Stemmata <on either side of the larval head, 6 or fewer>/

1. 6/

2. fewer than 6 <specify number>/

#219. The <mature> larval fronto-clypeus <of the head, extension>/

1. much extended forwardly/

2. not extended forwardly /

Morphological data on larvae are unsatisfactory, being mostly derived from Balfour-Browne’s keys and hopelessly non-comparative descriptive text.

#220. Frontoclypeal suture <of the larva> between frons and clypeus <presence>/

1. indistinct or absent/

2. distinct/

#221. The labrum and head capsule <of the larva, distinction>/

1. separated by a complete suture/

2. partly fused, with an incomplete suture/

3. completely fused, with no suture apparent/

#222. Apices of the mandibles <of the larva, toothing or lobing>/

1. with a single lobe or tooth/

2. bilobed or bidentate/

3. trilobed or tridentate/

4. multilobed or multidentate/

#223. The maxillary palps <of the larva, number of segments>/

segmented/

#224. The labium <of the larva, presence of a ligula>/

1. without ligula between the palps/

2. with a short ligula between the palps/

3. with a ligula at least as long as the palps/

#225. The labial palps <of the larva, number of segments>/

segmented/

#226. The mesothoracic legs <number of segments>/

segmented/

#227. The tarsi <of the larva, number of claws>/

1. 1-clawed/

2. 2-clawed/

#228. The mesothoracic legs <number of movable claws>/

1. with 1 movable claw/

2. with 2 movable claws/

#229. Visible abdominal segments <of the larva, number>/

#230. Tergum 9 of the abdomen <of the larva, ventral extension>/

1. entirely dorsal/

2. extending to the underside/

3. completely ventral <LW to pursue this>/

Larvae

#231. The larvae <whether aquatic>/

1. aquatic/

2. non-aquatic /

#232. The abdomen <of the larva, presence of functional abdominal spiracles>/

1. exhibiting functional abdominal spiracles/

2. without functional spiracles <these either lacking, or reduced and apparently non-functional>/

#233. The abdomen <of the larva, of functional spiracles on anterior segments>/

1. having functional spiracles on anterior segments/

2. with functional spiracles confined to the <posterior pair on> the eighth segment/

#234. The abdomen <of the larva, whether spiracles borne on lateral spiracular tubes>/

1. with the spiracles on the eighth segment borne at the ends of spiracular tubes/

2. with anterior and 8th-segmental spiracles borne at the ends of a series of spiracular tubes/

3. without spiracular tubes/

#235. The larvae <presence and form of gills>/

1. with dorsal, balloon-like tracheal gills on abdominal segments 1–8/

2. with long and narrow lateral gills on abdominal segments 1–7/

3. with long and narrow lateral gills on abdominal segments 1–9/

4. with ventral abdominal gill tufts on abdominal segments 1–3/

5. with ventral abdominal gill tufts on abdominal segments 1–4/

6. with anal <abdominal> gill tufts/

7. without <abdominal> gills <implicit>/

#236. The abdominal apex <of the larva, presence of a respiratory chamber>/

1. with a respiratory chamber, formed from the 8th and 9th terga and enclosing a pair of enlarged spiracles/

2. without a respiratory chamber/

#237. Abdominal tergum 8 <of the larva: armature, spiracles>/

1. bearing a single median process with a pair of spiracles at its apex/

2. bearing a single <simple> median process without apical spiracles/

3. bearing a pair of processes, each with an apical spiracle/

4. without amature <lacking processes>/

#238. The posterior segments <of the larva, presence of swimming hairs>/

1. with swimming hairs/

2. without swimming hairs/

#239. The last abdominal segment <of the larva, presence of cerci (urogomphi)>/

1. with cerci <urogomphi>/

2. without cerci/

#240. The last abdominal segment <of the larva, presence of a median spine>/

1. with a long, median spine <Hygrobia>/

2. without a long median spine /

#241. The larvae <whether predacious>/

1. predacious/

2. not predacious/

#242. The larvae <non-predaceous, diet>/

1. necrophagous/

2. feeding on dried animal remains/

3. phytophagous <live plant material: specify kinds>/

4. consuming decaying plant material <other than wood>/

5. eating dried plant material or stored plant products/

6. boring into living wood/

7. consuming rotting wood/

8. boring into dead wood/

9. mycetophagous <specify>/

10. coprophagous/

11. parasitic <specify>/

#243. The larvae <non-aquatic habitat>/

1. on living vegetation/

2. in decaying plant material/

3. in rotting wood/

4. in dried plant material/

5. in or under bark/

6. on lichens/

7. in fungi/

8. in dung/

9. in carrion/

10. in shed fur or feathers <in nests or burrows>/

11. associated with flowers/

12. under stones/

13. in stored plant products/

#244. <Descriptive comments on larvae>/

Worldwide and British representation

#245. <Species worldwide, number>/

species worldwide/

Estimates of genus and species numbers (derived mainly from assorted Internet sources) are often unreliable, but they should suffice for viewing British representation in a world context.

#246. Genera <worldwide, number>/

#247. <Number of species in Britain:>/

species in Britain/

From Pope (1977).

#248. Genera in Britain <number>/

#249. <Genera in Britain:>/

#250. Recorded from <distribution in the British Isles>/

1. Scotland/

2. Northern England/

3. South-west England and Wales/

4. South-eastern England <including East Anglia>/

5. Ireland/

Classification

#251. Suborder/

1. Adephaga/

2. Myxophaga/

3. Polyphaga/

See Unwin (1984), Lawrence et al (1999).

#252. Infraorder <of Polyphaga>/

1. Bostrichiformia/

2. Cucujiformia/

3. Elateriformia/

4. Scarabaeiformia/

5. Staphyliniformia/

#253. Superfamily <cf. Unwin, 1984>/

1. Bostrichoidea/

2. Buprestoidea/

3. Byrrhoidea/

4. Cantharoidea/

5. Caraboidea/

6. Chrysomeloidea/

7. Cleroidea/

8. Cucujoidea/

9. Curculionoidea/

10. Dascilloidea/

11. Dermestoidea/

12. Dryopoidea/

13. Elateroidea/

14. Eucinetoidea <Scirtoidea>/

15. Lymexyloidea/

16. Sphaeroidea/

17. Histeroidea/

18. Hydrophiloidea <Palpicornia>/

19. Scarabaeoidea/

20. Staphilinoidea/

21. Tenebrionoidea <Heteromera>/

See Unwin (1984), Lawrence et al (1999).

#254. <Family>/

1. Dryopidae/

2. Dytiscidae/

3. Elmidae/

4. Gyrinidae/

5. Haliplidae/

6. Heteroceridae/

7. Hydraenidae/

8. Hydrophilidae/

9. Hygrobiidae (Paelobiidae)/

10. Limnichidae/

11. Noteridae/

12. Psephenidae/

13. Scirtidae/

14. Spaeriidae/

#255. Subfamily <of Dytiscidae>/

1. Agabinae/

2. Colymbetinae/

3. Copelatinae/

4. Dytiscinae/

5. Hydroporinae/

6. Laccophilinae/

#256. Subfamily <of Hydrophilidae>/

1. Georyssinae/

2. Helophorinae/

3. Hydrochinae/

4. Hydrophilinae/

5. Spercheinae/

6. Sphaeridiinae/

#257. E.g., <scientific and common names of British representatives>/

Comments

#258. <General comments>/

#259. <Summary of generic characteristics>/

Miscellaneous

#260. Abbreviated taxon name:/

#261. <Illustrations:>/

#262. <Family or generic description>/

1. family description <implicit>/

2. generic description/


To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. British insects: water beetles. Version: 18th September 2012. http://delta-intkey.com’.

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