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

ABSTRACT

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.