OCCURRENCE OF DOUBLES COCOONS IN SERICIGENOUS INSECTS

The combination of two worms and rarely three larvae forming a single cocoon and subsequently metamorphosis into two or three pupae is a common phenomenon in scricigenous insects. Such cocoons are called double cocoons. The term double cocoons is a misnomer in so far as the terni ‘Double’ refers to the worms and not to the cocoons. This phenomenon ¡s of particulate occurrence in the Univoltine and Bivohine silkworm races and ro lesser degree in the cross breed races of the Uni and Bivoltinc races. The multi’ltjne races by themselves do not exhibit this phenomenon. As two worms are involment in spinning the cocoons the silk filament in a double cocoon criscross there by resuhing in a cocoon which does not lend itself to easy reeling as the continuity of the filament is lost and heavy breaks occur. However, a special quality silk known as “Dubion’ is reeled from the double cocoons by special techniques which is finding a good export market for fkintishing fabrics.An artemp has been made to review briefly the literatur available on the various aspects of the double cocoon formation and their proper utilization in silkworm seed production and reeling special type of silk fabrics and to suggest future avenues of investigation in the field to reduce the formation of double cocoon among the diticreni sericigenous insects and also to rest the relative merits thai the double cocoons could be safely used ¡n the preparation of commercial silkworm eggs in the silkworm seed production centres.