WASPS, SOCIAL AND SOLITARY 



fourteen days. Of course long before this time had ex- 

 pired the remnant of the caterpillar had become a dry, 

 dark- colored mass which looked little likely to tempt the 

 appetite, but the great larva ate away with unabated 

 relish, gradually acquiring the color and almost the 

 thickness of the caterpillar it had destroyed. 



Ammophila polita, which we have never seen in the 

 country, is very common in the sandy fields to the south 

 of Milwaukee. On the tenth of September, in bright 

 clear weather, we found half a dozen individuals work- 

 ing within a few rods of each other, their method being 

 similar to that of A. yarrowii, described by Dr. Willis- 

 ton, and having an especial interest, as it shows a transi- 

 tion stage between the wasps that provide the store of 

 food all at once and those that feed their young all 

 through the larval period. Urnaria rarely flies with her 

 prey ; but this wasp, although her caterpillars, are not 

 very much smaller, and she herself is no larger, carries 

 her booty lightly on the wing, alighting only occasion- 

 ally to run a few steps. She has to do more work than 

 urnaria, taking five or six caterpillars instead of two, 

 and this method of progression has the advantage of 

 rapidity. 



The first wasp that we saw was just alighting with a 

 medium-sized green caterpillar near a partly closed 



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