Ultrastructure of the Tarsus inOides decempunctatus(Billberg) (Coleoptera: Chrysomelidae)

Abstract

The ultrastructure of the tarsus of adult Oides decempunctatus (Billberg) (Coleoptera: Chrysomelidae) was examined using scanning electron microscopy. Structurally the tarsus consists of 5 tarsomeres and a pair of bidentate ungues on the pretarsus. The ventral surfaces of the 1st, 2nd and 3rd tarsomere are covered with dense adhesive setae. Each seta consists of two parts: a setal shaft and a modified apex. Three types of setae, viz. tapered setae, spatulate setae and discoidal setae, are identified based on the shape of the setal tip. The tapered setae are located at the edge of the 1st tarsomeres and on the whole 2nd tarsomeres of the male forelegs and mesolegs and on the whole 1st and 2nd tarsomere of the female legs and male metalegs. They are about 40–60 µm long and 4 µm broad at base, taper from base to apex with a curved, acute and hook-like apex and have a density of approximately 1 seta/100 µm2. The spatulate setae are located at the edge of the 3rd tarsomeres of the male forelegs and mesolegs and on the whole 3rd tarsomeres of the female legs and male metalegs. They are 55–85 µm long and 2.5–4.5 µm broad at base, have a spatulate terminal plate with 7–15 digits on margins, and have a density of approximately 1.5 setae/100 µm2. The discoidal setae are located in the centre of the 1st and 3rd tarsomeres of the male forelegs and mesolegs and are not present on female legs. They are about 45–80 µm long and 2.5–4.5 µm broad at base, have a discoidal terminal plate (7–9 µm in diameter) and have a density of one seta/100 µm2. These setae are presumed to function as adherence during climbing or mating activities of the beetles. The gland apertures and secretion solidification are also present on the ventral surfaces of the tarsus.