The visually controlled prey-capture behaviour of the European mantispid Mantispa styriaca

Mantispids (Mantispa styriaca) are predatory insects; on bright sunny days, they wait in ambush for insect prey. The prey is captured as soon as it is within reach by means of lightning-speed strikes with the powerful foreleg s, The strikes can take less than 60 ms, The mantispid accomplishes this al most as effectively as the larger praying mantis, which occupies a similar habitat, even though the praying mantis has apposition eyes with a high-res olution fovea, whereas the mantispid has unspecialized optical superpositio n eyes. Mantispa styriaca reacts to an item of prey when the latter covers a critical visual angle, The detection of prey immediately triggers adjustm ent reactions in the mantispid, which attempts to position the prey item in the visual field of both eyes and in the capture zone. Irrespective of the size of the prey, the capture reaction of the mantispid is always triggere d if the distance to the prey falls below a certain critical value. As indi cated by the analysis of individual video frames, immediately before an aim ed strike, the item of prey is always positioned exactly in the centre of t he binocular field of vision in the extended midsagittal plane of the manti spid's head. The strike may be triggered by the ommatidia of the left and r ight eyes, the lines of sight of which converge precisely on this region. T he principal conclusion to be drawn is that the prey-capture behaviour of t he mantispid appears to be based on a triangulation mechanism.