Elateriformia (Coleoptera) Larvae

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

DRYOPIDAE

Polyphaga: Elateriformia.

Dryopidae occur in most parts of the world, including New Zealand, but they are absent from Australia.

Dryopid larvae are most commonly found in damp soil, leaf litter and rotting vegetation; although they may inhabit riparian situations, no dryopid larvae are aquatic.

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.

Brown, H. P. (1991). Dryopidae (Dryopoidea), pp 399–401 in Stehr, F. W. (ed.), Immature Insects. Vol. II. Kendall Hunt: Dubuque, Iowa.

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; circular in cross-section; body, as viewed from above elongate and more or less parallel-sided. Vestiture consisting of fine hairs or setae only. Dorsal surfaces more or less heavily pigmented or sclerotized; generally smooth. Ventral surfaces more or less heavily 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 not strongly depressed and wedge-like anteriorly; posterior edge of head capsule distinctly 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 less than 0.15, or 0.15 to 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 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; without crenulate emargination. 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 broad when viewed from in front (perpendicular to plane of movement); trilobed or tridentate. Accessory ventral process of mandible absent. Incisor edge of mandible with 1 or 2 subapical teeth. Mesal surface of mandibular base simple or slightly expanded. Mandibular mola absent. Ventral mouthparts retracted. Cardo distinct and sclerotized; undivided; transverse to slightly oblique. Cardines or maxillary bases separated from each other by labium. Stipes longer than wide. Maxillary articulating area absent. 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 rounded or truncate; setose or spinose. Number of segments in maxillary palp four. First segment of maxillary palp without digitiform appendage. Labium consisting of prementum and postmentum. Mentum, postmentum or labial plate partly or completely fused with maxillae (sutures incomplete or absent). 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 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 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. Meso- and metaterga without sclerotized plates. Thorax without well-developed lateral tergal processes. Prosternum without armature. Mesocoxae or coxal lobes separated by less than 1 basal coxal diameter. 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 one. Thoracic spiracles biforous or bilabiate; 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 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 median process; median process on tergum 9 acute or narrowly truncate. Abdominal sternum 9 partly or entirely exposed; simple or apparently absent; not enclosed by sternum 8. Abdominal apex with ventrally 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, or posteroventrally oriented. Anal gill tufts absent. Anal hooks absent. 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, or much larger than others on abdomen; abdominal spiracle 8 lateral or dorsolateral, facing laterally, or dorsal, often near midline, facing posteriorly.


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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