The importance of pattern in visual attraction of Tabanus nigrovittatus Macquart (Diptera: Tabanidae)

Host-seeking females of Tabanus nigrovittatus primarily use visual cues to locate hosts and host mimics. The importance of various attributes of patterns was examined in the field in Massachusetts using black and white 2-dimensional panels. Panels with a square, circle or star of equal size were equally attractive, as were panels with stars with increasingly complex edges. In a series of panels with black circles of increasing size, attraction increased as the size of the circles increased. High contour density was not important in a series of panels with increasing size and decreasing number of patterns (squares or circles), and large patterns with simple edges were most attractive. Both light objects against a dark background and dark objects against a light background were highly attractive. The response of flies to objects with stripes indicated that stripes reduced attraction, possibly as a result of shape distortion. These results indicate that solid compact large objects with high contrast against the background were the most attractive, and that fine pattern detail was not important.