Scanning electron microscopic study of microfilaria and the third stage larva of Wuchereria bancrofti.

The surface structures of microfilaria and of the third stage larva of Wuchereria bancrofti were studied by scanning electron microscopy. Distinct features were observed that could be used for differentiating species of this parasite. Specifically, the sheath of microfilariae of W. bancrofti projected beyond the head. The head region of the microfilaria was composed of a cephalic cap with hook, mouth and amphidial opening, and its cuticle showed annulation. Spines were absent at the first transverse annulation, and the tail end showed a slight constriction. In the infective stage larva, characters which are used for differentiating species, such as the two bubble-like ventro-lateral papillae and one dorso-terminal papilla were rather similar to each other in size, but the grooves seen around the base were absent. A previously unreported feature of the third stage larva of W. bancrofti that was discovered in this study is a papilliform process on the left side of the posterior region, between the anus and the tail end.

Effects of a juvenile hormone analogue on the morphology and biology of Aedes scutellaris malayensis Colless (Diptera: Culicidae).

Effects of 2-methyl-9(4-isopropylphenyl)-2,6-dimethyl nonane, or MV-678, a juvenile hormone analogue, on Aedes scutellaris malayensis Colless were investigated under laboratory conditions (29 degrees +/- 2 degrees C and 86 +/- 3% RH). The MV-678 was tested against the first, second, third and fourth instar larvae. The concentrations used were 0.0032, 0.016, 0.08, 0.4 and 2.0 mg/l. The morphogenetic aberrations were determined and divided into 8 groups, among which they included (1) death larvae, (2) late fourth instar larvae before pupation, (3) larvae with pupae partly emerged, (4) white pupae, (5) brown pupae, (6) elephantoid pupae of which pupae with adults visible inside, (7) pupae with apparently adults partly emerged and (8) death adults. The percentage mortality rates were found to be relatively high in pupal and larval stages when they were treated with 2.0 mg/l. The LC50 values were 0.26, 0.175, 0.06 and 0.032 mg/l for the first, second, third and fourth instar larvae respectively. The effectiveness of MV-678 at 2.0 mg/l was about 11 days under the open air conditions (28 degrees +/- 2 degrees C and 72 +/- 3% RH). When the fourth instar larvae were treated with 0.4 and 2.0 mg/l of MV-678, the LC50 values were 3.1 and 7.1 days respectively.