In the present investigation, we studied the effect of some immunity responses of silkworm larvae such as, cellular immunity (total and differential haemocyte counts) against E. coli (G-) and B. thurengensis (G+) bacteria and also studied the effects of both E. coli and B. thurengensis at concentration of 1.5 ppm on the corpora allata (CA) activity during the last larval instar of B. mori to understand the effect of both bacteria on activation or inhibition of the CA activity and its relation with total and differential haemocytes counts