Notes on the Stages and the Biology of Baryodma ontarionis Casey (Coleoptera: Staphylinidae), a Parasite of the Cabbage Maggot, Hylemya brassicae Bouché (Diptera: Anthomyiidae)

Abstract

During investigations on the natural enemies of root maggots attacking Cruciferae, the beetle Baryodma ontarionis Casey was reared from puparia of the cabbage maggot, Hylemya brassicae (Bouché). This was not unexpected, for Gibson and Treherne (1916) had reported a similar occurrence; the staphylinid beetles reared at that time were identified by Casey (1916), who decided that they belonged to the verna group of Baryodma and assigned the name Baryodma ontarionis. Casey (loc. cit.) considered the species rather common and stated that it did not seem to resemble any European species; but Mr. W. J. Brown (in litt.), Systematic Entomology, Division of Entomology, Ottawa, who identified the beetles collected in 1950, is of the opinion that B. ontarionis is synonymous with Aleochara bilineata Gyll., tvhich attaclrs the cabbage maggot in Europe. Wadsworth (1915) dealt with the biology of A. bilineata, giving detailed descriptions of the immature stages. A study of the biology of B. ontarionis was carried out at the Belleville laboratory as part of n program of parasite introduction with the purpose in view of using the information to evaluate the beetle as a factor in the control of root maggots that are severe pests of cabbage, cauliflower, turnip, and radish.