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Boletín de la AeE

Boletín de la Asociación española de Entomología

 
inglés
Physical sensory ecology | Boln. Asoc. esp. Ent. 21 (Supl.): 80-81 | 1997
Digger wasp vs. cricket: Behavioural reactions of the prey due to the approach of the predator and their neurona! processing
W. Gnatzy
ABSTRACT
Anti-predator defense is a basic biological problem for insects as for other animáis. The defense strategies that have been evolved by insects are both diverse and remarkable. The fantastic attention to detail that nature has paid in the evolution of defensive traits provides ampie evidence of both the intensity and tile variety of selective pressures to which insects have been subjected.

Solitary wasps, like the palearctic digger wasp species Liris níger (Sphecidae), are predators of a rather special sort because of their specifícity as to prey (they hunt only crickets), the restriction of the predatory habit to the female and the consigrunent of the prey to tile nurture of the next digger wasp generation.

What happens, if a female digger wasp in ´´hunting mood´´ searches for a prey and suddenly draws cióse to a cricket? The most sfraightforward approach to defense is to flee. But we observed that only small crickets (< 1 cm) try to escape from an approaching Liris in huntingmood. Typical behavioural reactions of bigger larvae and adult crickets to the approach or to attacks of a female L. niger are: head-stand, stüt-stand, and defensive kick.

The mechanism by which the ´´head-stand´´ posture, for example, deters the attacking wasp is that it alters the apparent size and shape of the cricket prey. Furthermore, the postnre emphasizes the spiny, heavily sclerotized hindlegs of the cricket.

leased by the extremely wind-sensitive filifonn hairs on the cerci of the cricket, with no need for the predator to contact the cerci directly. In order to examine this, we implanted steel electrodes to one of the connectives leaving the cricket terminal ganglion. In this way we succeeded in recording neurograms from the axons of giant interneurons in the terminal abdominal ganglion of crickets, i.e. we were quasi able to listen in on the affairs in the nervous system of the cricket (as far as the information input from the rear end is concerned)

ln summary: Due to their hunting strategy of approaching the prey not ´´airborne´´ but ´´on foot´´. Liris females run under the cricket´s extremely sensitive cereal waming system, enabling the predator to come unnoticed closer to the prey.
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