Biological development after 5th instar among pure breed and hybrids of silkworm (<em>Bombyx mori</em> L.)

Abstract

This research was carried out to verify the duration of the rising up of caterpillar and the cocoon formation; duration of the cocoon formation to the emergency of the moth and the life span of the adult, as well as the medium weight of the green cocoon and liquid rate of silk, among two pure breeds - AJ1 (Japanese) and BC1 (Chinese) and two hybrids, from reciprocal crossing among two pure breeds - BC1 X AJ1 (H1) and AJ1 X BC1 (H2), in two different seasons: spring (S1) and autumn (S2). The hybrids and BC1 breed were superior to the pure race AJ1 making the cocoons, taking on average 3.4 days and 4.2 days, respectively (S1). The caterpillars grew in S2 were superior in 77.88% in their times of rising up and making the cocoon, in relation to S1. The hybrid H2 was better than the pure breeds in emergency of adult with average of 8.9 days, in S1. The females of the hybrid, survived an average of 3.8 more days than the pure breeds, in S1. In S2, H1 stood out in relation to the pure races, whose life span was superior in 9.6 days. For the males, in S2, the life span of H2 was 5.0 days. It was superior to the pure race AJ1 - 4.0 days. The hybrids and AJ1 presented heavier cocoons in 15.2% in relation to BC1 (S2) and liquid rate of silk was not significant in both seasons.