THE FEEDING-BEHAVIOR OF A SIT-AND-WAIT PREDATOR, RANATRA-DISPAR, (HETEROPTERA, NEPIDAE) - DESCRIPTION OF BEHAVIORAL COMPONENTS OF PREY CAPTURE, AND THE EFFECT OF FOOD-DEPRIVATION ON PREDATOR AROUSAL AND CAPTURE DYNAMICS

The components in the predatory behaviour of this typical sit-and-wait predator are described. The sequence of components follow a basic pattern, i.e. initial precapture posture, arousal, orientation, capture, consolidation of grip, exploration, injection of venom/enzymes, feeding, discard of prey. When tested with model prey of no nutritional value following increasing periods of fast R. dispar increased the initial exploratory time and the number of exploratory bouts before rejecting the prey. The predators arousal space is elliptical horizontally and almost circular vertically, the distance being greatest in front of the predator and decreasing to the rear. The strike and capture space of R. dispar is resticted to the space anterior to the predator and bounded by approximately 45.degree. either side horizontally and 90.degree. to -45.degree. (315.degree.) vertically. Both the arousal and strike space increase with food deprivation. The period of food deprivation significantly affects the strike distance up to a maximum of about 30 mm after a 120 hour fast. Presentation along some paths evokes more strikes, hits and captures than presentation along others, suggesting that there is an optimum region within the strike space where the capture efficiency is highest. Prey moving along the 0.degree. path in the horizontal plane or either the 0.degree. or 45.degree. path in the vertical plane, evoke the highest number of strikes, and hits in well-fed predators, while the highest capture efficiency occurs when prey are moved on the 0.degree. path. Following longer periods of fasting (> 72 hours) prey moved below the 0.degree. axis (Vertical Plane) along the -45.degree. (315.degree.) path evoke as many strikes as the 0.degree. and 45.degree. paths. Although dynamic, the capture space is limited by the reach of the raptorial legs, there being no lunge or pursuit. The capture efficiency is about 76% and unaffected by food deprivation.