The purpose of this study is to investigate the gene which controls the feeding response to calcium carbonate in the newly hatched larvae of the silkworm, Bombyx mori. Two silkworm strains, which either had or did not have a strong feeding response to calcium carbonate, were bred. Then, the crossings of F1 and BF1 generations between these two strains were carried out, and the individual feeding response to calcium carbonate in the larvae of each generation was examined. As a result, it was found that the strain with the capability of responding to calcium carbonate on feeding was recessive against the strain without it. Also, the single recessive gene that controls the feeding response to calcium carbonate was named ‘cacp gene (calcium carbonate preference gene)’. Next, in order to clarify the locus of the cacp gene, the genetic analysis was done by both methods based on the RFLPs (Restriction Fragment Length Polymorphisms) of cDNA clones, namely SLA (Scanning linkage analysis) and BCMAP (Mapping for Back Cross). It was found that the gene was linked with the ninth cDNA linkage group (RFLG 9) on the molecular gene map of the silkworm, and it was inferred that the locus of it was at a distance of 21.4 cM from the cDNA clone, m162, whiich located position 0 on RFLG 9.