Experimental Transfer of Abnormal "Sex-Ratio" in the Lady-Bird Beetle, Harmonia axyridis (PALLAS)(Coleoptera : Coccinellidae)

Abstract

An abnormal sex-ratio (SR) strain of H. axyridis (Pallas) which produced only females was selected and maintained until the 10th generation. Transfer experiments to detect the SR condition were carried out by microinjection of the supernatant from a homogenate of Sr pupae into normal pupae. The transfer of the SR agent(s) from the SR to the normal females was not observed when the latter mated on the 7th day after emergence, but it was observed in beetles which mated on the 30th day after emergence. The SR agent(s) were present in the supernatant and increased their infectious potency during the incubation period.