Description of the larval stages of Heterosternuta diversicornis (Sharp) (Coleoptera: Dytiscidae, Hydroporinae)

Abstract Description of structures of all three larval instars of Heterosternuta diversicornis (Sharp) is presented. The chaetotaxy and porotaxy of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi are discussed in detail. A close similarity between larvae of H. diversicornis, H. wickhami Zaitzev and H. cocheconis (Fall) is confirmed. All three species distinguish from the closely related species of the genus Neoporus Guignot by (i) a very short and constricted siphon, (ii) the primary setae FE8 and FE9 which are subequal in length to the maximum width of the metafemur (first instar), (iii) the absence of natatory setae on all tibiae and tarsi, and (iv) the contiguous position of the primary setae UR2 and UR3 on the urogomphomere 1.