Feeding strategies of the horseflies Hybomitra expollicata and Tabanus bromius in southern France

Blood-feeding success of female horseflies, Hybomitra expollicata Pandellé and Tabanus bromius L. (Diptera: Tabanidae), was studied. Bloodmeal weights of flies permitted different periods of residence on a horse's belly were estimated, and related to subsequent ovarian development and the number of mature eggs produced. Fitness gain per visit to a host (as estimated by the number of mature eggs produced) increased more rapidly with residence time on the host for H.expollicata than for T.bromius. H.expollicata inhibed blood more rapidly and, above a threshold bloodmeal size, produced a consistently higher number of eggs per unit weight of blood ingested. The feeding strategies of the two species are compared.