A SEM study of antennal sensilla in Maladera orientalis Motschulsky (Coleoptera: Scarabaeidae: Melolonthinae).

The external morphology of antenna and fine structure of its sensilla of Maladera orientalis were studied using scanning electron microscopy. The antenna consists of scape, pedicel, funicle and a club composed of three lamellae. Funicle has five, sometimes, four segments. Böhm bristles, three subtypes of sensilla chaetica, one subtype of sensilla trichodea, one subtype of sensilla coeloconica, four subtypes of sensilla basiconica, and one subtype of sensilla placodea were described. No sexual differences were found in number, type and distribution of sensilla on all antennomeres. The most notable feature of sensilla on antennae of M. orientalis is the presence of long and narrow strip-like sensilla placodea on both sides of all club lamellae. These porous sensilla placodea are slightly depressed below the lamella surface and tend to lie in parallel with the lamella axe. They are similar to sensilla placodea found in hymenopteran species but very different from those round plate-like sensilla placodea occurring on the lamellae of scarab beetles.