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.