Elateriformia (Coleoptera) Larvae

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J. F. Lawrence, A. M. Hastings, M. J. Dallwitz, T. A. Paine and E. J. Zurcher

BYRRHIDAE

(Including Syncalyptidae).

Polyphaga: Elateriformia.

Byrrhidae are almost entirely restricted to the temperate parts of the Northern and Southern Hemispheres.

Most species of Byrrhidae feed as larvae and adults on the leaves and rhizoids of mosses and liverworts (Bryophyta), but some have been recorded from lichens and others are known to attack the roots of various angiosperms, including grasses.

References

Böving, A. G. and Craighead, F. C. (1931). An illustrated synopsis of the principal larval forms of the order Coleoptera. Entomologica Americana (New Series) 1: 1–351, 125 pls.

Hudson, G. V. (1934). New Zealand Beetles and Their Larvae, 236 pp, 17 pls. Ferguson & Osborn: Wellington.

Johnson, P. J. (1987). Larval taxonomy, biology and biogeography of the genera of North American Byrrhidae (Insecta: Coleoptera), 253 pp. University of Idaho: Moscow, Idaho; MSc Thesis).

Lawrence, J. F. (1991). Byrrhidae (Byrrhoidea), pp 384–386 in Stehr, F. W. (ed.), Immature Insects. Vol. II. Kendall Hunt: Dubuque, Iowa.

Body. Length less than 3 mm to more than 15 mm. Body not broadly ovate and strongly flattened; relatively straight or only slightly curved ventrally, or strongly curved ventrally (c-shaped); circular in cross-section, or slightly flattened; body, as viewed from above elongate and more or less parallel-sided, or oblong to ovate, not parallel-sided. Vestiture consisting of fine hairs or setae only. Dorsal surfaces more or less heavily pigmented or sclerotized, or very lightly pigmented or sclerotized; generally smooth. Ventral surfaces very lightly pigmented.

Head. Head moderately to strongly declined (hypognathous); protracted or slightly retracted; not concealed from above by prothorax; narrower than thorax; not forming sclerotized, serrate, wedge-like plate. Head capsule not strongly depressed and wedge-like anteriorly; posterior edge of head capsule not or only slightly emarginate. Median epicranial region without longitudinal furrow. Epicranial stem moderately long; straight, not bent to the left. Frontal arms present; V-shaped or U-shaped; not joined anteriorly by transverse line; bases of frontal arms contiguous. Median endocarina absent or coincident with epicranial stem. Paired endocarinae absent or coincident with frontal arms. Number of stemmata six. Number of antennal segments three. Ratio of antennal length to head width 0.15 to 0.50. Sensorium(a) on preapical antennal segment present; shorter than apical segment. Sensorium(a) on preapical (or apical) antennal segment conical or palpiform. Apex of preapical antennal segment truncate, so that sensorium and apical segment arise together. Antennal base without eversible membranous lobe. Frontoclypeal suture distinct. Labrum separated from head capsule by complete suture. Epipharyngeal rods absent. Mouthparts not forming sucking tube. Mandibles symmetrical; opposable, at least slightly curving mesally at apex; not approximate, diverging and longitudinally divided; broad and stout or more or less wedge-like; without groove or perforation. Apex of mandible narrow when viewed from in front (parallel or oblique to plane of movement); with single lobe or tooth, or multilobed or multidentate. Accessory ventral process of mandible absent. Incisor edge of mandible simple, or with 1 or 2 subapical teeth. Mesal surface of mandibular base with brush of hairs or spines. Mandibular mola absent. Ventral mouthparts retracted. Cardo distinct and sclerotized; divided by internal ridge; transverse to slightly oblique. Cardines or maxillary bases separated from each other by labium. Stipes longer than wide. Maxillary articulating area present. Maxilla with articulated galea and fixed lacinia. Mala or galea consisting of a single segment, or 2-segmented. Apex of mala or galea rounded or truncate; setose or spinose. Apex of lacinia falciform; bearing 2 or 3 spurs or bifid spur. Number of segments in maxillary palp four. First segment of maxillary palp without digitiform appendage. Labium consisting of prementum, mentum and submentum. Mentum, postmentum or labial plate completely free or basally connate with maxillae. Postmentum or labial plate subquadrate or trapezoidal, with blunt posterior edge. Postmentum or labial plate not divided longitudinally. Ligula absent, or shorter than labial palp. Ligula simple, not bilobed; without tooth-like sclerome. Number of segments in labial palp two. Labial palps separated by more than width of first palp segment. Hypopharyngeal bracon present. Hypopharyngeal sclerome absent. Hypostomal region present (separating labium from thorax). Hypostomal rods absent. Ventral epicranial ridges present. Gula wider than long; gular sutures separate. Gula or gular region fused to labium. Occipital foramen not divided by tentorial bridge.

Thorax. Prothorax not or only slightly wider than abdomen; not longer than meso- and metathorax combined. Thoracic terga without patches of asperities; without rows of asperities or carinae. Protergum without sclerotized plates, or with 1 or more sclerotized plates. Meso- and metaterga without sclerotized plates, or with 1 or more sclerotized plates. Thorax without well-developed lateral tergal processes, or with well-developed lateral tergal processes. Prosternum without armature. Mesocoxae or coxal lobes separated by 1 to 2 basal coxal diameters. Thoracic legs articulated. Number of segments in mesothoracic leg five including pretarsus (claw). Number of segments in mesothoracic leg five or fewer including pretarsus (claw). Legs not highly reduced, more than 0.2 times as long as head width. Metathoracic leg about same size as mesothoracic leg. Meso- and metathoracic legs not forming stridulatory organ. Apical segment of leg acute and claw-like (or consisting of 2 claws). Number of movable pretarsal claws one. Number of setae on pretarsus two. Pretarsal setae lying side by side or obliquely situated. Thoracic spiracles biforous or bilabiate; not placed at ends of spiracular tubes.

Abdomen. Ratio of length of abdomen (without appendages) to length of thorax 1.2 to 2.0, or more than 2.0. Number of visible abdominal segments ten. Abdominal terga not extending laterally beyond edges of sterna, or extending laterally beyond edges of sterna; without patches of asperities; without rows of asperities. Abdomen without well-developed lateral processes, or with 1 pair of lateral processes on most segments. Abdominal tergum 3 without transverse dorsal folds or lobes; simple, not divided into transverse dorsal folds or lobes. Paired abdominal glands (openings or porous plates) absent. Dorsal, balloon-like tracheal gills absent. Long and narrow, lateral gills absent. Abdominal sterna without patches of asperities; without rows of asperities. Paired ventral prolegs (or asperity-bearing ampullae) absent. Ventral abdominal gill tufts absent. Abdominal tergum 8 without special armature. Abdominal apex without respiratory chamber. Abdominal segment 9 excluding appendages shorter than segment 8, or as long as or slightly longer than segment 8. Abdominal tergum 9 not forming articulated plate; completely dorsal; without paired processes or urogomphi; without median process or terminal disc, or with terminal disc. Abdominal sternum 9 partly or entirely exposed; simple or apparently absent; not enclosed by sternum 8. Abdominal apex without hinged operculum. Abdominal segment 10 without oval lobes separated by longitudinal groove; distinct and visible from above; without asperated, tubular holdfast organs. Paired pygopods on segment 10 shorter than wide. Anal region posteriorly or terminally oriented, or posteroventrally oriented. Anal gill tufts absent. Anal hooks absent, or 1 on each side. Anterior abdominal spiracles biforous or bilabiate. Abdominal spiracles not placed at ends of spiracular tubes. Eighth abdominal spiracles functional and about the same size as others on abdomen; abdominal spiracle 8 lateral or dorsolateral, facing laterally.

Illustrations. • Amphicyrta. • Cytilus.


The interactive key provides access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, and summaries of attributes within groups of taxa.

Cite this publication as: ‘Lawrence, J.F., Hastings, A.M., Dallwitz, M.J., Paine, T.A., and Zurcher, E.J. 1995 onwards. Elateriformia (Coleoptera) larvae: descriptions, illustrations, identification, and information retrieval for families and subfamilies. Version: 9th October 2005. http://delta-intkey.com’.

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