GENETICS AND EXPRESSION OF FUSED TARSI, A QUANTITATIVE TRAIT OF THE GERMAN-COCKROACH (DICYOPTERA, BLATTELLIDAE)

The fused tarsi trait (ftt) of the German cockroach, Blattella germani ca (L.), is characterized by fusion of the second and third tarsomeres . A stock was developed by selection in which the trait was expressed strongly on most legs of all individuals. Expression of the trait in t he selected stock and in standard genetic crosses was estimated by ana lyses using the following three methods: (1) individuals with at least one fusion between adjacent tarsomeres, (2) the number of legs with f used tarsomeres, and (3) the number of tarsomeres. In the last method, which gives the most reliable analysis of the trait, the degree of fu sion was classified into five grades by the number of tarsomeres: 5, w ild type; 4 3/4, slightly fused; 4 1/2, half fused; 4 1/4, almost fuse d; and 4, completely fused. Expression did not differ significantly be tween sexes, right and left legs, and fore-, mid-, and hindlegs. The F 1 was closer to wild type than to individuals in the selected ftt stoc k. Analysis of the F2 suggested that ftt is a quantitative trait contr olled by three gene pairs. Expression was suppressed in individuals he terozygous for T(9;10)/9;10Pw in the F1 and backcrosses to ftt. Test c rosses with T(9;10)/9;10Pw suggest that one of the factors controlling expression of ftt is located either on chromosome 9 or 10.