British Insects: the Families of Diptera

DELTA Home

L. Watson and M. J. Dallwitz

Character List

#1. <Nomenclature:>/

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

#2. <Common name(s) of family members:>/

#3. Life style <of species, whether parasitic or not; see Notes:>/

1. parasitic <in either larval or adult stages, or both>/

2. non-parasitic /

Note the essential distinction to be made between “parasitic”, referring as here to the general life-style of a species; and the same term when it relates to the precise feeding habits of the insects in their larval and adult stages (q.v.). The different concepts are often confused in entomological literature.

#4. <When parasitic> on <animal groups>/

1. humans/

2. mammals other than humans/

3. birds/

4. bats/

5. slugs and snails/

6. millipedes/

7. spiders/

8. woodlice/

9. Homoptera/

10. Lepidoptera/

11. Coleoptera/

12. bees and other Hymenoptera/

13. bees only/

14. Odonata/

15. other Diptera/

16. Orthoptera/

17. Arthropods in general/

18. Annelid worms/

Adult insects

#5. <Size of adults:>/

1. very small <less than 4 mm long>/

2. small <4–8 mm long>/

3. medium-sized <8–15 mm long>/

4. large <15 mm or more long>/

#6. <Body shape of adults:>/

1. slender-bodied/

2. robustly-built/

#7. <Body hairiness>/

1. hairy bodied/

2. not hairy bodied/

#8. <Whether shining, black, rather hairy flies>/

1. shining, black, rather hairy flies/

2. not shining black/

#9. <Whether adults winged:>/

1. winged /

2. wingless/

#10. <Leg form of adults:>/

1. stilt-legged <legs long and thin>/

2. not stilt-legged <legs of about average length and thickness> /

#11. The legs <whether brittle and readily shed>/

1. readily shed/

2. not readily shed /

#12. The face in lateral view <whether deeply hollowed>/

1. deeply excavated between the antennae and the edge of the mouth/

2. not deeply excavated between the antennae and the edge of the mouth/

#13. The back of the head <occiput, flattened or rounded>/

1. rounded, with fine pale hairs below/

2. markedly flattened above, without fine pale hairs below/

#14. Antennae <number of segments>/

segmented/

‘2–6’ (recorded for many Brachycera sensu lato) probably usually means ‘3’.

#15. Antennae <length and thickness>/

1. long and threadlike/

2. short and stout/

#16. Antennae <whether simple>/

1. ‘simple’ <basic structure filiform, moniliform or linear, the segments more or less all alike; not evidently ‘reduced’ or ‘modified’. Usually longer than the head and thorax>/

2. ‘modified’ <not filiform, variously reduced and/or complicated, with markedly differentiated segments. Usually shorter than the thorax>/

#17. Antennae <whether terminal segment annulated>/

1. having the terminal segment annulated/

2. with a non-annulated terminal segment/

#18. Antennae <whether aristate>/

1. aristate/

2. not aristate/

‘Arista’: in this context, a bristle-like extension of the terminal antennal segment (in practice, usually of the third antennal segment of Brachycera), with or without hairs or cilia, which may itself be segmented.

#19. The <antennal> arista <when aristate, whether apical>/

1. apical/

2. dorsal <including ‘sub-apical’>/

#20. The <antennal> arista <whether forked at the tip>/

1. characteristically, conspicuously forked at the tip <via its main stem and the last hair>/

2. not forked at the tip/

#21. The second antennal segment <whether with an external groove>/

1. distinctly grooved <cleft> above/

2. not <externally> grooved /

This character, featured prominently by Colyer and Hammond as characterising the calypterate families, is here treated as unreliable for identification on the advice of D.M. Unwin.

#22. The second antennal segment when viewed from the outside <whether partly obscuring the third>/

1. with a triangular projection extending partway over the third and often with an upper and a lower bristle/

2. normal, with no extension over the third/

#23. The third <antennal> segment <elongation>/

1. elongated/

2. not elongated/

#24. Ptilinal suture <presence>/

1. <and lunule> clearly defined/

2. absent or weakly defined <and the lunule often weakly defined or absent> /

‘Ptilinum’: an inflatable sac, exhibited above the base of the antennae by (Brachycera-) Muscomorpha Schizophora, which is used by the emerging insect to rupture the puparium. Its former presence is subsequently detectable on the head, as a conspicuous groove between the face and the orbits. In groups where it is found (viz., the Calyptratae and Acalyptratae), the ptilinal suture is continuous with a crescentic depression (the ‘lunule’) over the bases of the antennae. A lunule, unaccompanied by a clear ptilinal suture, also occurs in some Aschiza.

#25. Ocelli <presence>/

1. present/

2. absent/

‘Ocellus’: a simple eye. Many Diptera exhibit 2 or three, towards the back of the head between the compound eyes.

#26. Ocelli <when present, number>/

#27. The top of the head <prominence>/

1. with a marked depression between the eyes, within which the ocellar triangle projects/

2. with no marked depression between the eyes/

#28. Ocellar bristles <presence>/

1. present/

2. absent/

#29. <Compound> eyes <whether meeting above the antennae>/

1. asymmetric, nearly or quite connected above the antennae <holoptic>/

2. rounded, well separated/

#30. Lower orbital bristles <presence>/

1. present/

2. absent/

#31. Lower orbital bristles <carriage>/

1. incurved/

2. curved forward/

#32. Post-vertical orbital bristles <presence>/

1. present/

2. absent/

#33. Post-vertical orbital bristles <carriage>/

1. convergent/

2. parallel/

3. divergent/

#34. Mouthparts <whether functional>/

1. functional /

2. non-functional/

It may or may not be safe to treat ‘functional’ as implicit, but for the present this risky device has not been implemented.

#35. Mouthparts <whether piercing>/

1. adapted for piercing <as well as sucking>/

2. non-piercing <e.g., suctorial only>/

For numerous families, the detailed constitution of mouthparts (“trophi”) is not mentioned in any of the descriptions seen.

#36. Mandibles <presence>/

1. present/

2. absent/

#37. Mandibles <whether represented by piercing stylets>/

1. represented by long, slender, piercing stylets/

2. not in the form of long, slender, piercing stylets/

#38. The maxillary palps <number of segments>/

segmented/

#39. The maxillary palps <porrect or drooping>/

1. porrect/

2. drooping/

‘Porrect’: extending more or lesshorizontally, or ascending, rather than drooping.

#40. Vibrissae <presence>/

1. present/

2. absent/

‘Vibrissae’: extra-large bristles, arising from the angles at the sides of the mouth in many Brachycera sensu lato.

#41. Thorax <dorsum: presence of complete dorsal suture>/

1. with the dorsal suture <just in front of the wing bases> continuous across the middle/

2. without a continuous dorsal suture /

‘Dorsal suture’: a transverse groove on the sides or back and sides of the thorax, between its front (prescutum) and middle (scutum) - i.e., in front of the wings. It may be complete across the back of the thorax, discontinuous and visible only laterally, or vestigial or absent.

The dorsal suture is (riskily?) assumed to be discontinuous or absent from the numerous families for which it is not mentioned in the literature seen. Where explicitly stated to be absent in the literature, it has been explicitly encoded as such.

#42. The dorsal suture <shape>/

1. deeply V-shaped/

2. deeply U-shaped/

3. neither V-shaped nor U-shaped /

‘Dorsal suture’: a transverse groove on the sides or back and sides of the thorax, between its front (prescutum) and middle (scutum) - i.e., anterior to the wings.

#43. Thorax <differentiation of posterior calli>/

1. with well defined posterior calli/

2. without well defined posterior calli/

‘Posterior calli’: a pair of swellings, or callosities, one at each hind corner of the back of the thorax (dorsum). Especially pronounced in Calyptratae.

#44. Postscutellum <whether well developed>/

1. present and well developed/

2. absent or weakly developed/

#45. Posterior division of pronotum <presence of long bristles>/

1. with one or more long bristles/

2. without long bristles/

#46. Hypopleural bristles <under the posterior thoracic spiracle: presence>/

1. present/

2. absent/

‘Hypopleural bristles’: bristles borne on the hypopleura, i.e., on each side of the thorax, above the insertion off the hind leg and below the posterior thoracic spiracle.

‘Hypopleuron’: the hindmost, lower-lateral thoracic plate.

#47. The post-humeral bristle <situation>/

1. located on the thorax higher than or level with the pre-sutural bristle/

2. located lower on the thorax than the pre-sutural bristle/

#48. Wing venation <whether complete, with reference to cells>/

1. complete, in the sense of exhibiting 1st and 2nd basal, anal and discal cells/

2. incomplete, in the sense of lacking one or more of the <basal, anal, discal> cells/

#49. Wing veins <or veins and branches> reaching the margin <number>/

#50. Wing veins <or veins and branches> reaching the margin between the anal cell and the lower fork of vein 3 <number>/

#51. Wing vein 7 <the hindmost vein, whether reaching the margin>/

1. reaching the margin/

2. falling short of the margin/

#52. Wings <presence of discal cell>/

1. with a discal cell/

2. without a discal cell <i.e., with no cross vein separating it from the 2nd basal cell>/

‘Discal cell’: a cell (of wide occurrence) bounded by veins 4 and 5. Encoded here as absent in cases where it is described as “confluent with the second basal cell” (i.e., where there is no delimiting cross-vein).

#53. Wings <presence of a sub-apical cell>/

1. with a <more or less closed> subapical cell <bounded by veins 3 and 4>/

2. without a sub-apical cell/

‘Sub-apical cell’: a cell, at or near the wing apex, bounded by veins 3 and 4. Restricted to about a dozen families.

#54. Wings <presence of closed anal cell>/

1. with a closed anal cell/

2. without a closed anal cell/

‘Anal cell’: a cell (of wide occurrence) bounded by veins 5 and 6. It is sometimes very small.

#55. The <closed> anal cell <length>/

1. relatively long <extending more than halfway to the wing margin>/

2. short <extending less than halfway to the wing margin>/

#56. Wings with <number of cells between vein 3 and the anal cell>/

cells between vein 3 and the anal cell/

#57. Wings <fourth posterior cell open or closed>/

1. with the fourth posterior cell open/

2. with the fourth posterior cell closed/

#58. The costa <whether broken>/

1. unbroken/

2. with one break/

3. with two breaks/

‘Costa’: the stout nervure constituting the front edge of the wing.

This widely quoted character is here treated as unreliable for identification, on the advice of D.M. Unwin.

#59. The costa <extension>/

1. extending around the entire wing/

2. not extending around the entire wing /

‘Costa’: the stout nervure constituting the front edge of the wing.

#60. The costal vein <thickening>/

1. markedly thickened/

2. not markedly thickened/

#61. Sub-costa <whether identifiable>/

1. apparent <at least partially free of vein 1>/

2. absent or only dubiously identifiable/

Data on the sub-costa mainly from Colyer and Hammond's family descriptions, rather extensively extended from their illustrations and those of Colless and McAlpine.

#62. Sub-costa <whether reaching the costa>/

1. short and ending free/

2. usually long and ending in the costa/

#63. Sub-costa <where readily identifiable, pathway and development>/

1. reaching the costa independently of vein 1/

2. joining vein 1 more or less where it joins the costa/

3. distally forked, to join both the costa and vein 1/

4. joining vein 1 well short of the costa/

5. terminating blind <not joining vein 1, and falling short of the costa>/

Data on the sub-costa mainly from Colyer and Hammond's family descriptions, rather extensively extended from their illustrations and those of Colless and McAlpine.

#64. The leading edge <wing> veins <whether stronger than the rest>/

1. markedly stronger than the rest/

2. not noticeably stronger than the rest /

#65. Wings <whether with a sharp bend in vein 4>/

1. exhibiting a sharp bend in vein 4/

2. without a sharp bend in vein 4/

Vein 4 is generally identifiable as the one constituting the forward margin in the discal cell (q.v.).

#66. Wings <whether exhibiting a ‘vena spuria’>/

1. exhibiting a ‘vena spuria’/

2. without a ‘vena spuria’ /

‘Vena spuria’ (false vein): a thickening of the wing membrane between and parallel with the third and fourth veins, which is not joined to any vein. Confined to and characteristic of Syrphidae.

#67. Wing vein 1 <whether hairy>/

1. with hairs on its upper side/

2. bare/

#68. Wing vein 3 <whether distally forked>/

1. distally forked/

2. not forked/

#69. The fork of wing vein 3 <form and position>/

1. broad, its lower branch reaching the wing margin well below the apex/

2. narrow, its lower branch reaching the wing margin near the apex/

#70. Wing vein 4 <whether distally forked>/

1. forked distally/

2. not forked/

#71. Wing vein 4 <length>/

1. very short, extending little beyond the end of the first basal cell/

2. extending far beyond the end of the first basal cell/

#72. Wing vein 6 <present or absent>/

1. present/

2. absent/

#73. Wing vein 6 <whether reaching the margin>/

1. reaching the wing margin/

2. falling short of the wing margin/

#74. Wing vein 7 <presence or absence>/

1. present/

2. absent/

#75. Wing vein 7 <whether reaching the margin>/

1. reaching the wing margin/

2. falling short of the wing margin/

#76. Media and cubitus veins <whether connected>/

1. connected via a cross vein or by a fusion/

2. not connected by a cross-vein or a fusion/

#77. Media vein <whether distict or fused basally with radius>/

1. with a distinct basal section/

2. fused basally with the radius for a short distance/

#78. Media-cubitus and radius-media cross-veins <presence>/

1. both present, almost in one line/

2. not both present, media and radius being fused/

#79. <Media-cubitus and media-radius cross-veins>/

1. m-cu <media-cubitus> well before r-m <radia-medius>/

2. m-cu and r-m cross-veins close/

#80. Wings <whether lower calypter much enlarged>/

1. with a well developed lower calypter <= thoracic squama>/

2. with the lower calypter much reduced or absent/

‘Calypters’ (‘squamae’): flap-like appendages at the hind-bases of the wings, or attached to the thorax close to the wing bases. Not to be confused with the ‘alula’, which is often present as a conspicuous lobe in the hind margin of the wing distal to the calypters.

The upper calypter (alar squama) occurs at the base of the wing; the lower calypter (thoracic squama) is attached to the thorax.

#81. Wings <patterning>/

1. patterned/

2. unpatterned <clear> /

#82. The legs <whether banded brown and yellow>/

1. with brown and yellow bands/

2. without brown and yellow bands/

#83. The front femora <whether with a spine beneath>/

1. with a short stout spine beneath which is readily distinguishable from the other bristles/

2. without a conspicuous spine beneath/

#84. The hind femora <whether thickened and with spines beneath>/

1. thickened, with two rows of spines beneath/

2. not thickened with spines beneath as in Megamerinidae/

#85. Tibiae <whether spurred>/

1. spurred/

2. without spurs/

#86. Tibiae <at least the hind tibiae, presence of a dorsal pre-apical bristle>/

1. with a dorsal pre-apical bristle/

2. without a dorsal pre-apical bristle/

#87. Hind tibiae <strong bristles in the basal 4/5>/

1. with strong bristles in the basal 4/5 <‘strong’ = at least as long as the diameter of the tibia; excluding single, ‘dorsal pre-apical bristles’, q.v.>/

2. without strong bristles in the basal 4/5 <i.e., with or without short bristles, and any strong bristles other than single ‘dorsal pre-apical bristles’ confined to the proximal end>/

#88. Feet <pads>/

1. with a triple pad beneath the tarsal claws <comprising the two pulvilli plus a pulvilliform empodium>/

2. without a triple pad <with two pads representing the pulvilli only, or these represented by claws>/

#89. The hind tarsi <basal segments>/

1. having the basal three or four segments flattened and dilated/

2. normal <not flattened and dilated>/

#90. Abdomen <whether constricted basally>/

1. constricted basally <fly wasp-waisted>/

2. not constricted basally/

#91. Visible abdominal segments <number>/

#92. <Feeding habits of adults: note the deliberate distinction here between the habits of adults and larvae>/

1. parasitic/

2. predatory/

3. neither parasitic nor predatory/

Note the essential distinction to be made between “parasitic”, referring to the general life-style of a species (q.v.); and the same term when it relates, as here, to the precise feeding habits of individuals. The different concepts are often confused in entomological literature. See the character concerned with the feeding habits of larvae for further comments.

In practice, the distinction between “parasitic” and “predatory” is less clear than text-book definitions usually suggest. The larvae of many Diptera and Hymenoptera, in particular, contradict the common assertion that highly specialised parasitism does not result in the death of the host (with the added, teleological supposition that to do so is inimical to the long term survival of the parasitic species). In fact, many dipteran and hymenopteran larvae universally described as “parasitic” are highly adapted to keep the host alive only for as long as it is needed as a source of food, before ultimately killing it.

Larvae and pupae

#93. The larvae <whether aquatic>/

1. aquatic/

2. terrestrial <i.e., not habitually submerged>/

#94. The larvae <feeding habits. See Notes>/

1. phytophagous <feeding on living plant material>/

2. saprophagous <feeding on decaying organic matter>/

3. coprophagous/

4. consuming stored produce/

5. mycophagous/

6. predatory/

7. parasitic/

8. developing within the mother, being nourished via a greatly developed ‘acessory gland’, before leaving to pupate/

Note the essential distinction to be made between “parasitic”, referring to the general life-style of a species (q.v.); and the same term when it relates, as here, to the precise feeding habits of individuals. The different concepts are often confused in entomological literature.

In practice, the distinction between “parasitic” and “predatory” is less clear than text-book definitions usually suggest. The larvae of many Diptera and Hymenoptera, in particular, contradict the common assertion that highly specialised parasitism does not result in the death of the host (with the added, teleological supposition that to do so is inimical to the long term survival of the parasitic species). In fact, many dipteran and hymenopteran larvae universally described as “parasitic” are highly adapted to keep the host alive only for as long as it is needed as a source of food, before ultimately killing it.

#95. The larvae <parasitic, whether endo- or ecto-parasitic>/

1. endoparasitic/

2. ectoparasitic/

#96. The larvae <phytophagous, whether gall-forming>/

1. forming galls/

2. not gall-forming/

#97. The larvae <development of head>/

1. eucephalic <with a distinct head capsule>/

2. hemicephalic <with a weak or incomplete head capsule>/

3. acephalic <with no indication of an external head skeleton>/

#98. The pupae <presence of a puparium>/

1. enclosed within a <hardened> puparium <the pupal integument delicate>/

2. without a puparium <the pupal integument sclerotized>/

‘Puparium’: a persistent, hardened and modified, usually barrel-shaped, ovoid or globular derivative of the cuticle of the third larval instar, functioning as a cocoon enclosing a thin-skinned pupa. In a few families (e.g Stratiomyidae), the last larval skin persists in unmodified form (‘transitional puparia’).

Comments

#99. <General comments:>/

Classification

#100. Suborder/

1. Nematocera/

2. Brachycera/

#101. Division <of Nematocera>/

1. Tipulomorpha/

2. Bibionomorpha/

3. Psychodomorpha/

4. Ptychopteromorpha/

5. Culicomorpha/

#104. Superfamily <of Brachycera>/

1. Xylophagoidea/

2. Tabanoidea/

3. Stratiomyoidea/

4. Nemestrinoidea/

5. Asiloidea/

6. Empidoidea/

7. Platypezoidea/

8. Lonchopteroidea/

9. Syrphoidea/

10. Nerioidea/

11. Diopsoidea/

12. Conopoidea/

13. Tephritoidea/

14. Lauxanioidea/

15. Scyomyzoidea/

16. Opomyzoidea/

17. Carnoidea/

18. Sphaeroceroidea/

19. Ephydroidea/

20. Hippoboscoidea/

21. Muscoidea/

22. Oestroidea/

British representation

#105. <Number of species in Britain>/

species in Britain/

#106. Genera <in Britain, number>/

#107. <Genera in Britain:>/

Miscellaneous

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

#109. Abbreviated taxon name:/

#110. <Illustrations>/


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: the families of Diptera. Version: 1st January 2012. http://delta-intkey.com’.

Contents