Amylase isozyme based three multivoltine viz., N+p, Np, N+ $p^{cho}$ and two bivoltine-D6+p, D6p syngenic lines (Syn. L) were developed from germplasm (GP) stocks Nistari (N) and D6 respectively. haemolymph isozyme pattern at pH 7.0 and 8.5 depicted a total 11 number (Am $y_{1 to 6}$ at pH 7.0 and Am $y^{l to 5}$ at pH 8.5) of native proteins (NP) of various sizes are amylase isozyme expressers. Among eleven NPs, two NPs of 770 kDa (Am $y^{6}$ at pH 7.0) and 376 kDa (Am $y^3$ at pH 8.5) are $alpha$-amylase expressers and remaining NPs of 370, 364, 350, 329 and 274 kDa at pH 7.0 and 206, 292, 416, 725 kDa at pH 8.5 are $eta$-amylase expressers. Accordingly, digestive juice amylase isozyme pattern at aforesaid pH also depicted a total number of 10 NPs (Am $y^{1 to 5}$) at each pH 7.0 and 8.5 are amylase expressers of which NP of 387 kDa (Am $y^4$ at pH 7.0) and 780 kDa (Am $y^{5}$ at pH 8.5) are a-amylase expresser. Remaining NPs of 338,297 ＆ 216 kDa at pH 7.0 and 370, 341, 329 ＆302 kDa at pH 8.5 are $eta$-amylase expresser. Recurrent backcross lines (RBL) viz., N+pRBL and NpRBL were developed through introgression of high shell weight character (a multigenic trait) to be used further for congenic line (Con. L) development and to understand any association with introgressed character. Isozyme pattern in haemolymph of RBLs depicted only one $alpha$-amylase of 770 kDa at pH 7.0 and 376 kDa at pH 8.0 with three and four respective $eta$-amylase bands but in bivoltine lines numbers of $eta$-amylase bands vary between 1 to 2 at aforesaid pH. Variability was also observed in digestive juice of multivolitine and its RBLs but bivoltine lines express null activity at both pH except appearance of one very week $alpha$-amylase band D6+p at pH 8.5. Overall study suggests that not a single NP at both pH is common for expression of any band of amylase isozyme i.e., a totally different set of proteins are the amylase isozyme expresser at specific pH and no molecular factor of amylase is associated in developed RBLs which showed improvement on survival, single cocoon shell weight (SCSW) and single filament length over receptor parents.s.s.s.