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In the present investigation, an attempt was made to study the effect of brushing time, silkworm hybrids and mulberry varieties for food dynamics and commercial trait expression. The experiment was laid out in factorial-completely randomized block design with eight treatments and three replications and the analysis of treatments was worked out by analysis of variance technique. The treatments comprised of two brushing time (early i.e. 1 st of March and late i.e. 20 th of March), two hybrids (PO 3 ×ND 5 and SH 6 ×NB 4 D 2) and two mulberry varieties (China white and Tr-10). The brushing time, silkworm hybrids and mulberry varieties influenced significantly most of the food dynamic and cocoon traits. Observations made for food dynamics and commercially important traits indicated that, food ingestion and digestion, conversion of ingested and digested food, approximate digestibility, production efficiency of cocoon shell, efficiency of cocoon production, percentage of cocoon shell weight, effective rate of rearing (by weight and by number), single cocoon weight, single shell weight, shell ratio percentage, fibroin and sericin content, total filament length, non-breakable filament length and renditta were significantly higher for early brushing time, PO 3 ×ND 5 and China white. Thus, only one commercial rearing is possible with brushing time of early i.e. 1 st of March for hybrid PO 3 ×ND 5 fed on China white mulberry variety for spring rearing in the field at farmer's level for better prospects of bivoltine sericulture in subtropical plains.

Synthesis of new-gene combinations by genetic manipulation is one of the powerful tools in exploiting the commercial qualities of plants and animals. The fundamental aim of silkworm breeding is to get robust and sturdy silkworm larvae for easy rearing and production of quality cocoon crop. Bivoltine breeds and hybrids excel in quality and productivity but do not display the crop stability. The main reason attributed to such instability is that the bivoltine breeds/hybrids suffer badly in adverse conditions. In the present study, an attempt was made to evaluate twenty-eight bivoltine hybrids raised by involving half (8×8) diallel set of bivoltine breeds including four hypersericigenous (PO 1 , PO 3 , ND 2 and ND 5) and four thermotolerents (Udhey-1, Udhey-3, Udhey-4 and Udhey-6) along with ruling bivoltine hybrid, SH 6 ×NB 4 D 2 in order to identify the thermotolerent, adaptable bi×bivoltine silkworm hybrids suited for subtropical climate. Observations were made on eight economically important traits namely, larval weight, crop weight, single cocoon weight, single shell weight, shell ratio, average filament length, non-breakable filament length and denier. The data was analyzed using Evaluation index (E.I.) method. Ten hybrid combinations recorded mean evaluation index (E.I.) values of >50 ranging from 51.13 to 63.35, whereas, control scored E.I. value of 49.22 only. Two hybrid combinations, ND 5 ×PO 1 (63.35) and ND 2 ×Udhey-6 (60.12) recorded Average E.I. value >60 for all the characters under subtropical conditions.