Ultrastructural Morphology of Tarsus of Aspidomorpha dorsata (F.) (Coleoptera: Hispidae)

Abstract

The ultrastructural morphology of the tarsus of the adult beetle, Aspidomorpha dorsata (F.) (Coleoptera: Hispidae), is described for the first time, using scanning electron microscopy observations. The tarsus of A. dorsata consists of 5 tarsomeres and the distal pretarsus consists of a pair of ungues. The foretarsus and midtarsus are similar to each other whereas the hindtarsus exhibits specialization. The ungues, which articulate dorsally at the distal end of the tarsus, are broad basally (about 169 - 178 μm long and 126 - 133 μm wide), gradually taper into an acute apex over apical half, with the surface of the ungues being rough dorsally and longitudinally grooved innerly and ventrally. There are three small, parallel, accessory ungues (about 35 - 80 μm long) on the ungues. The surface of the accessory ungue is smooth. The ventral surface of the first, second and third tarsomeres is covered with dense adhesive setae. Each seta consists of two parts: a setal shaft and a modified apex (terminal plate). Four types of adhesive setae, viz. the pointed setae, the spatulate setae, the discoidal setae and the drop-shaped setae, are recognized based on the shape of the setal tip. The pointed setae are about 29 - 39 μm long, have acute, pronged and curved tips and are found on tarsomeres I and II of the hind legs and on the edge of tarsomeres I and II of the fore and middle legs. The spatulate setae are about 34 - 55 μm long, have spatulate, pronged and curved terminal plates and are present on tarsomere III of three pairs of legs. The discoidal setae are about 23 - 24 μm long, have discoidal tips and are found on tarsomeres I and II of fore and middle legs. A few drop-shaped setae are found on tarsomere II of three pairs of legs. The distribution of the 4 types of setae is different on the 3 pairs of legs. This suggests that the fore, middle and hind legs exhibit different adhesive functions during the climbing.