Effect of seasonality and perisulfakinin on engorgement by Tabanus nigrovittatus (Diptera: Tabanidae) in the laboratory

The horse fly Tabanus nigrovittatus Macquart (Diptera: Tabanidae), a bematopbagous 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. The percentage of flies engorging a bloodmeal in the laboratory throughout the season was recorded, and here we demonstrate that the percentage of flies that are blood feeding fluctuates, leading to a decrease in flies 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 flies injected with one nanomole of perisulfakinin were inhibited from blood feeding by 45-60%. The satiation of feeding reported here is in agreement with the previous research by using nonhematophagous species. When groups of flies were injected with 10 nmol of perisulfakinin, the percentage of flies engorging was increased relative to the sham-injected flies, although not significantly. The stimulation of engorgement by sulfakinin has not previously been demonstrated, and its mode of action remains unclear.