A Tergal Abnormality in the German Cockroach, Blattella germanica (L.)1

During the investigation of a wing mutation in the German cockroach (Cochran & Ross 1961), sib-matings of some of these mutant roaches were made for several generations. From certain of these crosses there appeared roaches in which the body was twisted in a most unusual but consistent manner. Thus far attempts to mate twisted males and females have been unsuccessful. Twisted cockroaches have been successfully crossed with normal cockroaches, however, and normal-appearing offspring were produced. Most of these roaches were accidentally lost prior to maturation, but the trait has continued to appear in the inbred line which first produced it. More recently a few specimens have been found in other inbred lines as well. To date 15 twisted roaches have appeared in the original inbred line (3 in the F1, 3 in the F2, and 9 in the F3). A genetical basis for the trait is thus indicated, but as yet the mechanism is not clear. Therefore, the present note is primarily a morphological description of the abnormality.