Elateriformia (Coleoptera) Larvae

DELTA
Home

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

THROSCIDAE

(= Trixagidae).

Polyphaga: Elateriformia.

Throscidae is a widely distributed family.

Larvae of the European Trixagus dermestoides (Linnaeus) occur in the soil and feed on mycorrhizal fungi on roots, but several North American specimens have been found in decaying wood and grass tufts.

References

Becker, E. C. (1991). Throscidae (Elateroidea), pp 418–419 in Stehr, F. W. (ed.), Immature Insects. Vol. II. Kendall Hunt: Dubuque, Iowa.

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.

Burakowski, B. (1975). Development, distribution and habits of Trixagus dermestoides (L.), with notes on the Throscidae and Lissomidae (Coleoptera, Elateroidea). Annales Zoologici, Warsaw 32: 375–405.

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

Head. Head prognathous or slightly declined; protracted or slightly retracted; not concealed from above by prothorax; narrower than thorax; not forming sclerotized, serrate, wedge-like plate. Head capsule strongly depressed and wedge-like anteriorly; posterior edge of head capsule not or only slightly emarginate. Median epicranial region without longitudinal furrow. Epicranial stem absent or very short. Frontal arms absent. Median endocarina absent or coincident with epicranial stem. Paired endocarinae absent or coincident with frontal arms. Number of stemmata zero. Number of antennal segments two, or three. Ratio of antennal length to head width less than 0.15. Sensorium(a) on preapical antennal segment present; shorter than apical segment, or as long as or longer 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 absent or vaguely indicated. Labrum completely fused to head capsule (suture absent); without crenulate emargination. Epipharyngeal rods absent. Mouthparts not forming sucking tube. Mandibles symmetrical; non-opposable, straight or curving laterally at apex; not approximate, diverging and longitudinally divided; flattened and more or less triangular; 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. Accessory ventral process of mandible absent. Incisor edge of mandible simple. Mesal surface of mandibular base simple or slightly expanded. Mandibular mola absent. Ventral mouthparts retracted. Cardo absent, indistinct or membranous. Cardines or maxillary bases separated from each other by labium. Stipes longer than wide. Maxillary articulating area absent. Maxilla with single, fixed mala. Mala or galea consisting of a single segment. Apex of mala simple, not cleft; or galea falciform; or galea glabrous. Inner apical angle of mala simple. Number of segments in maxillary palp three. First segment of maxillary palp without digitiform appendage. Labium consisting of prementum and postmentum. Mentum, postmentum or labial plate completely or almost completely connate with maxillae. Postmentum or labial plate subquadrate or trapezoidal, with blunt posterior edge. Postmentum or labial plate not divided longitudinally. Ligula shorter than labial palp. Ligula simple, not bilobed; without tooth-like sclerome. Number of segments in labial palp two. Labial palps contiguous or separated by less 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 absent. Gula absent; gular sutures absent. Gula or gular region separated from labium by suture. 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. Thorax without well-developed lateral tergal processes. Prosternum with rod-like sclerotization. Mesocoxae or coxal lobes separated by more than 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, or highly reduced, less 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 annular-biforous (?); not placed at ends of spiracular tubes.

Abdomen. Ratio of length of abdomen (without appendages) to length of thorax more than 2.0. Number of visible abdominal segments ten. Abdominal terga not extending laterally beyond edges of sterna; without patches of asperities; without rows of asperities. Abdomen without well-developed lateral processes. 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. Abdominal tergum 9 not forming articulated plate; extending onto ventral surface; with paired processes or urogomphi; without pit between urogomphi; without median process or terminal disc. Ratio of length of urogomphus to basal width of tergum 9 less than 0.2. Urogomphi fixed at base; unsegmented; not bifurcate and without accessory processes; dorsally or posterodorsally oriented; separated by more than 2 basal widths. 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; concealed from above, sometimes membranous or more or less fused to segment 9, or distinct and visible from above; without asperated, tubular holdfast organs. Paired pygopods on segment 10 absent. Anal region posteroventrally oriented. Anal gill tufts absent. Anal hooks absent. Anterior abdominal spiracles annular-biforous (?). 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.


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’.

Contents