Raptorial Forelegs Research Articles

The predatory strike of the praying mantis, Tenodera aridifolia sinensis

Analyses of time-lapse video recordings of free-moving, seven-(last larval) instar and adult praying mantids, Tenodera aridifolia sinensis (Sauss.) of both sexes have revealed that this insect's predatory strike is more variable than has been reported for preparations that are tethered or restricted in their movements. Differences were found in four aspects of prey-catching behaviour. Compared to tethered or movement restricted preparations, free-moving T. sinensis initiate strikes from both longer and shorter mantis-prey distances, lunge over a wider range of distances, and can capture prey at shorter mantis-prey distances. Further, free-moving T. sinensis can successfully capture prey which is initially struck by the tibia as well as the femur. These findings increase our understanding both of mantis hunting behaviour, and the mechanical limitations of the mantis' raptorial forelegs.

Prey capture in mantids: The role of the prothoracic tibial flexion reflex

The role which the prothoracic tibial flexion reflex plays in prey catching by the mantis Tenodera aridifolia sinensis (Sauss.) is examined. This reflex is elicited both by tactile stimulation of the movable spines on the ventro-medial border of the raptorial foreleg femur, and by pulling against the tibia. The reflex elicited by spine stimulation is inhibited when the ipsilateral tarsus is resting on the substrate, but is not if the tibia rests on the substrate after removal of the tarsus. Immobilizing the femoral spines by covering them with paraffin wax eliminates the ipsilateral tibial reflex to spine stimulation but not to tibia pulling. If either the right or left set of femoral spines are immobilized, the waxed foreleg fails to grip prey, and is readjusted around captured prey more frequently than the normal leg. If both sets of femoral spines are immobilized, the mantid's ability to successfully capture prey is impaired but not eliminated. It is concluded that proprioceptive feedback from the movable femoral spines and the tibiae play roles in, but neither are solely responsible for maintaining a continuous grip on prey captured by T. sinensis.

Distance and Size Discrimination in a Water Stick Insect, Ranatra Linearis (Heteroptera)

ABSTRACT The role of vision in distance, position and size discrimination in prey capture has been investigated in normal adult water stick insects (Ranatra linearis L. : Heteroptera) and in ones with one eye covered. Both monocular and intact Ranatra were able to discriminate between two targets subtending the same angle but presented at different distances. They usually chose the target nearer to their foreleg claws. Although monocular subjects undershot more often than controls, they could still estimate distance correctly. When presented with two different-sized targets at the same distance, both monocular and intact subjects usually preferred the larger target within a 1°–10° range, even though monocular animals chose the larger object less consistently. They were able to distinguish between two targets differing in size by only 1 °. Asymmetrical presentations of two identical targets stressed the importance of the central position. Intact animals always preferred the target nearer their midline. These data also revealed the unexpected ability of Ranatra to strike accurately at two targets or prey items simultaneously. When two identical targets were presented simultaneously and symmetrically, aims were directed at both targets, and one was grasped by each raptorial foreleg, thus indicating an absence of confusion.