BLOOD-FEEDING STRATEGY OF HAEMATOBIA-IRRITANS (DIPTERA, MUSCIDAE)

The economic impact on livestock production by Haematobia irritans (L. ) is estimated to approach $1 billion per year in North America. Howev er, there is little information regarding the blood-feeding strategy u sed by these insects. Information presented here shows that horn fly s aliva interferes with the normal coagulation response as measured by t he recalcification time assay. The relative anticoagulant activity on a per-gland basis was more than or equal to that reported for Simulium vittatum Zetterstedt, a common hematophagous black ny that also feeds on cattle. However, unlike S. vittatum, H. irritans salivary factors do not inhibit platelet aggregation using apyrase and have no detectab le vasodilative activity. In this regard, the horn ny is strikingly di fferent from blood-feeding species in the lower Diptera and shows a mu ch more limited repertoire of antihemostatic factors.