Feeding responses of the horsefly, Tabanus nigrovittatus , to phagostimulants

Wild caught horseflies, Tabanus nigrovittatus Macq. (Diptera, Tabanidae), were presented solutions of 0.15 MNaCl at 37°C containing various concentrations of ATP, ADP, AMP, adenosine, phytic acid or 2,3‐diphosphoglycerate in an artificial feeding apparatus. The insects fed upward through a Para‐film M® membrane. ADP (ED 50 35 μM) was more potent than ATP (ED 50 112 μM) and AMP (ED 50 382 mUM). All of these diets were deposited in the midgut, an indication that the flies were in the ‘blood feeding’ mode. Adenosine caused only 23% gorging at 1 mM. Phytic acid caused only 10% gorging at 1 mM and 2,3‐diphosphoglyceric acid had no activity at 0.6 mM. Flies would feed only in highly reflective cages under high levels of light intensity (1200–1500 lux) at the membrane surface.