Our recent studies have revealed that calcium carbonate (CaCO3) could elicit the feeding response from the newly hatched larvae of the silkworm, Bombyx mori. This paper was intended as an investigation of the genetic aspects of the feeding response to CaCO3 in the larvae. Two strains, which either had or did not have a strong feeding response to CaCO3, were bred among numerous varieties by repeating interbatch-selections. Then, the crossings of F1, F2, and BF1 generations between these two strains were carried out, and the feeding response to CaCO3 in each generation was examined. Calcium carbonate was added to the basal diet consisting of cellulose powder, agar, and distilled water. The diets thus prepared were given to the newly hatched silkworm larvae. Fifty larvae, which derived from eggs of the same maternal moth, were assigned to each test group, and the experiment was repeated ten times with the eggs of ten moths. After rearing the larvae on the diet at 25°C in the dark for 72 h, the preference of larvae for CaCO3 in the diet was estimated by the consumption of the diet, that is, the number of feces excreted since the start of feeding. Both diet consumptions in reciprocal F1 hybrids were equivalent, and they were less than in the parental strain showing an appreciable feeding response to CaCO3. The result clearly showed that the strain with the capability of responding to CaCO3 on feeding was incompletely dominant against the strain without it. Moreover, it was inferred from the result of the feeding experiments that the genetic factors regarding the feeding response to CaCO3 in the newly hatched larvae consisted of a major gene and its modifiers on the autosomal chromosome.
In silkworm breeding and to maintain practical breeding resources, it is important to weigh the cocoon shell and pupa. We developed a new weighing system using a PC operating with Windows and Microsoft Excel. In the new system, two electronic balances were connected to the computer with a RS-232C interface to weigh the shell and pupa simultaneously. In comparison with a similar system using MS-DOS and N88-BASIC, our system can be used more broadly because it uses an ordinary personal computer installed with Microsoft Excel. In addition, the data obtained can be processed much more easily than with the other system.