Influence of juvenile hormone analogue and insulin applied at third and fourth instar on some larval and cocoon characters in bombyx mori L.

Context: Juvenile hormone and insulin prolongs the larval duration in mulberry silkworm thereby extending the feeding period which results in an increase in cocoon weight and cocoon shell weight. The larval treatment with Juvenile Hormone analogue could be utilized to increase silk production. Objective: The objectives of the study is to find out the influence of a Juvenile Hormone analogue, Manta and human insulin to the larval instars of silkworm, Bombyx mori (L) (PM x CSR2) on larval growth, development and cocoon characters. Materials and Methods: The disease free layings of polyvoltine race (PM x CSR2) of silkworm, B. mori were used for the study. The acetone solution of manta was used for topical application to third and fourth instar larvae at 36 hours after second and third moult at the rate of 8 ml solution application to the group of 100 larvae through hand sprayer. For insulin treatment 100 g fresh mulberry leaves were soaked in 300 ml of aqueous solution of insulin for half an hour. The first feeding after treating the larvae with manta consisted of insulin treated leaves. The pre-cocooning parameters such as larval duration, larval weight, silkgland weight and the post cocooning parameters such as female and male cocoon weights and their shell weights and shell ratio were calculated. Results: The results indicate the larval duration and larval and silkgland weight significantly increased after treatment with manta or manta followed by insulin treatments. The results of the present study suggest that the treatment with manta followed by insulin yields heavier cocoons and cocoon shells in both the sexes than those obtained after treatment with manta or insulin. Conclusion: It can be suggested that the treatment with Manta followed by insulin may be utilized to increase silk production by increasing the heavier larva, cocoon, shell. Keywords: Bombyx mori; silkworm; Juvenile hormone; Manta; insulin. DOI: http://dx.doi.org/10.3329/jbs.v18i0.8775 JBS 2010; 18(0): 49-52