PHYSIOLOGY, BIOCHEMISTRY, AND TOXICOLOGY Effect of Seasonality and Perisulfakinin on Engorgement by Tabanus nigrovittatus (Diptera: Tabanidae) in the Laboratory

The horse ßy Tabanus nigrovittatusMacquart (Diptera: Tabanidae), a hematophagous insect, is a nuisance pest along the Atlantic Coast. A description of the engorgement pattern throughout the season is lacking in the literature for this species. Thepercentageof ßies engorging abloodmeal in the laboratory throughout the season was recorded, and here we demonstrate that the percentage of ßies that are blood feeding ßuctuates, leading to a decrease in ßies engorging as the season ends. Additionally, three recent nonhematophagous insect studies demonstrated that sulfakinins, a vertebrate homologue of cholecystokinin, function in feeding inhibition as a satiety factor. We found that groups of ßies injected with one nanomole of perisulfakinin were inhibited from blood feeding by 45Ð60%. The satiation of feeding reported here is in agreement with the previous research by using nonhematophagous species. When groups of ßies were injected with 10 nmol of perisulfakinin, the percentage of ßies engorging was increased relative to the sham-injected ßies, although not signiÞcantly. The stimulation of engorgement by sulfakinin has not previously been demonstrated, and its mode of action remains unclear.