4 Psyche [Vol. 88 
Fig. 1: Attack of an adult acridid grasshopper (Oedipodinae) by a Prionyx parkeri 
wasp. The wasp uses both the strong mandibles and long, powerful legs, to firmly 
hold the prey and prevent escape. The grasshopper tries (in vain) to push away the 
wasp with both powerful hind legs by applying strong pressure on the points where 
the wasp is anchored (head and one fore leg). Several drops of regurgitated repelling 
fluid are indicated by arrows. The wasp already assumes the appropriate posture for 
the first paralyzing sting, delivered in the throat of the victim. 
quantitative observations were almost impossible. At times the 
grasshoppers stayed put instead of escaping, for no apparent reason. 
Attack of the wasp does not necessarily follow detection of a 
suitable prey, however, since hunting wasps go through periods of 
temporary refractoriness (Steiner 1962, 1976, 1978, 1979). This 
considerably complicates the study of possible effects of prey- 
defenses on the wasps. 
b) Observations in captivity 
The same responses were also recorded in captivity. Flying away 
