RESPONSES TO MOVING SMALL-FIELD STIMULI BY THE PRAYING-MANTIS, SPHODROMANTIS-LINEOLA (BURMEISTER)

Adult, female praying mantises, Sphodromantis lineola (Burmeister), we re presented with mechanically driven or computer generated stimuli in a series of seven experiments in order to test several hypotheses reg arding visual prey recognition. When presented with a series of square black and white computer generated stimuli against a white background , mantises performed the highest rates of predatory behavior in respon se to those stimuli with a greater proportion of black versus white pi xels (i.e., those that produced larger luminance decrements). Higher r esponse rates to computer generated stimuli that produced larger lumin ance decrements were also seen when the stimuli were irregularly shape d or consisted of two small synchronized stimuli. Mantises responded c haracteristically to mechanically driven stimuli that were camouflaged to match the background against which they moved, preferring small (v s. large) squares and rectangles that were elongated parallel (vs. per pendicular) to their direction of movement. Finally, response rate to a small, preferred, mechanically presented or computer generated stimu lus was suppressed by a concurrent large-field stimulus in inverse pro portion to the distance between the two stimuli. This phenomenon is ch aracteristic of systems that include phasic lateral inhibitory circuit s. All of these results are consistent with the existence of a movemen t detector visual sub-system, as found in other orthopteromorph insect s such as acridid grasshoppers and cockroaches.