1981] 
Steiner — Anti-predator Strategies 
3 
Eritettix variabilis Bruner; (2) for Tachysphex wasps, small acridid 
nymphs of: Oedipodinae, mostly Conozoa carinata Rehn and also 
a few Trimerotropis pallidipennis p. (Burm.); Cyrtacanthacridinae, 
a few Psoloessa delicatula and an occasional Melanoplus sp., 
Derotmema sp., Rehnita sp. Rather similar but un-determined 
grasshoppers were used in the Oregon study, in captivity. The grass- 
hoppers were provided either ad libitum, or in staged encounters. 
Observations were mostly continuous, with “all occurrences” 
sampling of wasp-prey interactions. Precise quantifications were 
difficult or impossible because initial stages of encounters were 
often sudden and unpredictable. Generally speaking proof of effects 
of escape-defense reactions is often very difficult to establish (e.g. 
Edmunds 1974, p. 240). This study is basically descriptive. 
Total observation times were; (1) for captive P. parkeri in the 
Arizona study about 178 h over a period of 30 observation days 
(X = about 6 h-day) and in the Oregon study about 142 h for 14 
observation days (X= about 6 V 2 h-day); (2) for captive Tachysphex 
wasps in the Arizona study about 224 h for 37 observation days (X = 
about 6h-day) and in the Oregon study about 224^ h for 35 
observation-day (X = 6!4 h-day). 
Results: Description of Responses, Conditions 
Common responses: escape by jumping (flying) away, 
staying put = first line of defense. 
a) Field observations 
Visually hunting Prionyx (parkeri?) wasps were observed in the 
short and sparse grassy vegetation, characteristic of the upper 
Sonoran desert grassland. Acridid grasshoppers were abundant, 
particularly Oedipodinae such as Mestobregma plattei rubripenne 
(Bruner) adults, also found stored in the nests of these wasps. The 
most common response to wasps approaching or pouncing was a 
very sudden, even startling, escape by jumping (Fig. 5a) and flying 
away (Fig. 5b). The bright flash of the colorful banded wings came 
in sharp contrast with the sudden disappearance from sight, after 
landing (crypticity: Fig. 5c). The wasps seldom followed the escap- 
ing grasshoppers in flight, but occasionally did so (Fig. 5b) and even 
managed to cling to them in mid air and to deliver stings before 
landing. Most stung grasshoppers were apparently caught by sur- 
prise or at the preparatory stages of escape. Close range and 
