Description of the preimaginal stages of Enochrus (Hugoscottia) variegatus (Steinheil, 1869) and E. (Methydrus) vulgaris (Steinheil, 1869) (Coleoptera: Hydrophilidae), with emphasis on larval morphometry and chaetotaxy

Abstract

The morphology of the preimaginal stages of Enochrus Thomson (Coleoptera: Hydrophilidae) is investigated. Descriptions and detailed illustrations of the egg cases, all three larval instars, and pupae of the Neotropical species E. (Hugoscottia) variegatus (Steinheil, 1869) and E. (Methydrus) vulgaris (Steinheil, 1869) are presented. The larval morphology of these species is studied on the basis of chaetotaxic and morphometric analyses of selected structures (head capsule, head appendages and legs). A key to larval instars of Enochrus is also presented. The larval instars can be separated by means of morphometry and chaetotaxy of the head capsule, cephalic appendages and legs. Several characters common to the five subgenera known as larvae are discussed. The primary chaetotaxy plan for the maxilla is updated on the basis of observations made on Enochrus larvae as well as on additional hydrophilid taxa.