Elateriformia (Coleoptera) Larvae

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

DASCILLIDAE

(Including Karumiidae).

Polyphaga: Elateriformia.

Dascillidae occur in western North America, the West Indies, Eurasia, southern South America, Africa, southeastern Asia, the Sunda Archipelago and eastern Australia; they are not commonly collected.

Larvae of Dascillus and probably most Dascillidae occur in the soil and may be collected beneath stones. They feed on plant roots and other organic matter in the soil, breaking food up with complex epipharyngeal and hypopharyngeal plates, similar to those found in Scarabaeoidea. At least some Karumiinae are associated with termites, but the larval feeding habits of these are unknown.

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.

Lawrence, J. F. (1991). Dascillidae (Dascilloidea), pp 369–370 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; circular in cross-section, or 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 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 distinctly emarginate. Median epicranial region without longitudinal furrow. Epicranial stem absent or very short; 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 zero. Number of antennal segments two, or three. Ratio of antennal length to head width 0.15 to 0.50, or more than 0.50. Sensorium(a) on preapical antennal segment present; as long as or longer than apical segment. Sensorium(a) on preapical (or apical) antennal segment dome-like. 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 partly fused to head capsule (suture incomplete); without crenulate emargination. Epipharyngeal rods absent. Mouthparts not forming sucking tube. Mandibles asymmetrical; opposable, at least slightly curving mesally at apex; not approximate, diverging and longitudinally divided; broad at base and narrow at apex; without groove or perforation. Apex of mandible broad when viewed from in front (perpendicular to plane of movement); bilobed or bidentate. Accessory ventral process of mandible present. Incisor edge of mandible with 1 or 2 heavily sclerotized retinacula. Mesal surface of mandibular base with mola or basal processing area. Mandibular mola present; mola without hyaline lobe or brush at base; molar surface with numerous fine ridges. Prostheca a simple, membranous lobe. Prostheca or basal mandibular process narrow with acute or narrowly rounded apex; glabrous. Ventral mouthparts retracted. Cardo distinct and sclerotized; externally divided; 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. 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 three. 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 shorter than labial palp. Ligula bilobed. Number of segments in labial palp two. Labial palps separated by more than width of first palp segment. Hypopharyngeal bracon present. Hypopharyngeal sclerome divided into 2 parts or consisting of more than 1 sclerite. Hypostomal region present (separating labium from thorax). Hypostomal rods present (1 pair); moderately long but not extending to posterior edge of head; diverging posteriorly. Ventral epicranial ridges absent. 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; with transverse row(s) of asperities (sometimes forming carinae) on metathorax only. Protergum with 1 or more sclerotized plates. Meso- and metaterga with 1 or more sclerotized plates. Thorax without 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 four or more. Thoracic spiracles cribriform; 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; with rows of asperities on 1 or more segments. Rows of abdominal tergal asperities transverse; single; one per segment. 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; completely dorsal; without paired processes or urogomphi, or 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; without asperated, tubular holdfast organs. Paired pygopods on segment 10 absent. Anal region posteriorly or terminally oriented. Anal gill tufts absent. Anal hooks absent. Anterior abdominal spiracles cribriform. 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. • Dascillus.


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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