Feeding responses of the horsefly, Tabanus nigrovittatus, to phagostimulants

In studies in the USA, wild-caught adults of Tabanus nigrovittatus Macq. were presented with solutions of 0.15 M NaCl 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 Parafilm M membrane. ADP (ED50 35 µM) was more potent than ATP (ED50 112 µM) and AMP (ED50 382 µM). All of these diets were deposited in the mid-gut, 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.