Follicle developmental stages in blood-seeking horseflies (Diptera: Tabanidae) in Alberta, Canada.

Abstract

Developmental stages of terminal follicles in 1855 females of 11 Hybomitra species collected in Manitoba fly traps and from around horses were recorded. I believe all of these flies were seeking blood meals. Between 76% and 97% of the nullipars in anyone species had yolk in the terminal oocytes. The stage of follicle development in a parous fly varied with the fly's physiological age (i.e., uniparous, biparous, sac-stage, “yellow bodies”) and the physiological character (i.e., anautogenous, autogenous) of the species to which it belonged. Within every physiological age class, significantly more flies with “yellow bodies” than those in the sac-stage had yolk in the terminal oocytes. Significantly more unipars of anautogenous species than unipars of autogenous species had yolk in the terminal oocytes. Biparous flies were relatively rare. The need of more than 1 blood meal for some pars to develop a batch of eggs is suggested.