Elateriformia (Coleoptera) Larvae
Scirtidae is a widely distributed family, but the greatest diversity occurs in the temperate parts of the Northern and Southern Hemispheres.
Larval Scirtidae are usually found in aquatic situations, normally in stagnant water, such as ponds, tree holes, marshes or bogs; however some larvae have been collected in damp rotting wood well away from water. They are detritus-feeders and have a complex filter-feeding mechanism for gathering and concentrating very small particles in liquid suspension. Enlarged terminal spiracles are used to obtain air at the water surface.
Beier, M. (1949). Koerperbau und Lebensweise der Larve von Helodes hausmanni Gredler (Col. Helodidae). Eos 25: 49–100.
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.
Costa, C., Vanin, S. A. and Casari-Chen, S. A. (1988). Larvas de Coleoptera do Brasil, vi + 282 pp. Museu de Zoologia, Universidade de Sao Paulo: Sao Paulo.
Hannappel, U. and Paulus, H. F. (1991). Some undetermined Helodidae larvae from Australia and New Zealand: fine structure of mouthparts and phylogenetic position, pp 89–128 in Zunino, M., Bellés, X. and Blas, M. (eds), Advances in Coleopterology. Associación Europea de Coleopterología: Barcelona.
Hudson, G. V. (1934). New Zealand Beetles and Their Larvae, 236 pp, 17 pls. Ferguson & Osborn: Wellington.
LeSage, L. (1991). Helodidae (Eucinetoidea), pp 366–369 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; slightly flattened; 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 not or only slightly 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, or distinctly separated. Median endocarina absent or coincident with epicranial stem. Paired endocarinae absent or coincident with frontal arms. Number of stemmata one, or two, or three. Number of antennal segments five or more. Ratio of antennal length to head width more than 0.50. Sensorium(a) on preapical antennal segment absent, or present; shorter than apical segment. 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 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; 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 present. Incisor edge of mandible simple. 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 fixed, rigid process and brush of hairs. Prostheca or basal mandibular process narrow with acute or narrowly rounded apex, or broad with obtusely angulate apex; generally pubescent. 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 present. Maxilla with fixed galea and lacinia. Mala or galea consisting of a single segment. Apex of mala or galea rounded or truncate; bearing comb-hairs or spatulate hairs. Apex of lacinia falciform; bearing single spur. 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 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. 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 absent. Ventral epicranial ridges absent. 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 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 less than 1 basal coxal diameter to 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. 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 reduced and non-functional or absent.
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 nine, or eight. Abdominal terga 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 with respiratory chamber. Abdominal apex with respiratory chamber formed from 8th and 9th terga and enclosing pair of enlarged spiracles. Abdominal segment 9 excluding appendages shorter than segment 8. Abdominal tergum 9 not forming articulated plate; completely dorsal; without paired processes or urogomphi; without median process or 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; 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 present. Anal hooks absent. Anterior abdominal spiracles reduced and non-functional or absent. Abdominal spiracles not placed at ends of spiracular tubes. Eighth abdominal spiracles only functional pair on abdomen; abdominal spiracle 8 lateral or dorsolateral, facing laterally.
Illustrations. • Scirtes.
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’.