INTRODUCTION 5 



compared with what can be accomplished under the rigorous 

 and indefinitely variable control of the laboratory. Still 

 results of considerable value have been obtained by simple 

 field experimentation as will be apparent to the reader of 

 the ingenious studies of Fabre, the Peckhams and the Raus. 



Although the activities of only a few hundred solitary 

 wasps have been carefully- observed, we may be sure that 

 every one of the 10,000 described species has its own pecu- 

 liar behavior. In the non-parasitic forms this appears as 

 a complex cycle, the more important component minor 

 cycles, or phases of which are the digging or construction 

 of the nest, the capture and stinging of the insect or spider 

 prey, oviposition and the sealing of the nest entrance. But 

 the sequence and details of these cycles is subject to great 

 specific and sometimes to considerable individual variation. 

 Thus the sequence of the three first cycles in many species 

 of Sphegids is nest prey egg, but in Psammocharids it 

 is commonly prey nest egg, and in the Eumenids nest 

 egg prey. This is also the sequence in social wasps (Po- 

 listes, Vespa, etc.). In parasitic species the behavior is, 

 of course, peculiarly modified in adaptation to that of the 

 host. 



In their interpretation of wasp behavior the Raus agree 

 essentially with nearly all previous investigators as could 

 be shown by quotations from Marchal, Picard, Bordage, 

 Adlerz, the Peckhams, Hartman and others. Most of the 

 activities can be readily interpreted as chain-reflexes, or 

 "instincts" in the usual biological sense of the term. They 

 are relatively fixed or stereotyped and undoubtedly heredi- 

 tary and therefore represent the most ancient and most 

 solidified complex of the behavioristic cycle. But there 

 stand out from this complex many activities which are much 

 less mechanized and of such a nature as to demonstrate 

 that the wasps possesss emotions and associative memory, 



