Comparative study on cocoon economic characters in three different races of the silkworm, Bombyx mori (Linnaeus) infected with uzifly, Exorista sarbillans (Wiesemann)

The cocoon weight, length and width, shell weight, cocoon-shell ratio, filament length and fi lament weight decreased in the races PM and NB₄D₂ and their hybrid PM x NB₄D₂ silkworms after uzi infestation. The cocoons of NB₄D₂ were more affected than in PM race and PM x NB₄D₂. The floss percentage greatly increased in NBDrace, but decreased in PM and PM x NBDand was significant in PM race. The denier increased in both the races and their hybrid, which was significant in NB₄D₂ and PM x NB₄D₂ but non-significant in PM race. The uzifly infection could cause grater damage to the cocoons of NB₄D₂ race followed by PM race and PM x NB₄D₂ hybrid.