192 WASP STUDIES AFIELD 



time, so why did they not come about before the hole was 

 opened? Probably just because the flies could not scent the 

 hopper through an inch or more of well-packed earth. So 

 if the fly, with its highly specialized olfactory organs, 

 cannot scent the contents of the nest when it is closed with 

 earth, how can we have the audacity to suspect that uni- 

 cinctus finds her way to the burrows by the sense of smell 

 alone? Of course, you may say, it is possible that mother 

 Priononyx, when carrying out the earth, leaves her taint 

 upon it. Perhaps so, but even if she does, in this case the 

 condition of the hopper and parasites showed that the nest 

 had been sealed for at least three days, and surely any 

 taint that Priononyx could leave at her doorway would, in 

 three days of wind and weather, have been reduced to a 

 minimum. Granting that Priononyx does leave an odor, 

 we would again have to prove that Stizus has the power to 

 perceive it in so delicate a degree. It is hard to believe that 

 she locates the nest by the grasshopper .odor, for the field 

 is at that time of year constantly overrun by hordes of 

 grasshoppers, and certainly she cannot by scent pick out 

 a buried one which is just like all the others except that 

 it is paralyzed. 



Thus it seems, from the evidence at hand, that the greater 

 part of the responsibility in discovering the hidden nests 

 falls upon the sense of sight, although it is almost beyond 

 belief that any one sense could be developed to such a de- 

 gree of sensitiveness. 



The highly specialized instinct of Stilus to get the 

 hopper only after it is buried is worthy of note. The hop- 

 per lies fully exposed for a long period awaiting burial, 

 during which time Stizus ignores it, but suspiciously visits 

 and revisits the hole. Would it not have been less complex 

 if her instinct had been so developed as to lead her to seek 



