THE SPIDER RA VISHERS. 125 



CHAPTEK XII. 



THE SPIDER RAVISHERS. 



Pompilus and Agenia. 



Plated L, figs. 1, 2 and 7; V.; X., figs. 6, 7 and 8; XII., fig. 5: 



XIII, fig. 1. 



While Ammophila feeds her larva upon caterpillars, and 

 Bembew, after the manner of the social wasps, feeds her young 

 from day to day on dead flies, the Pompilidae, so far as their 

 habits are known, all prey upon spiders. The family is a large 

 one in the United States, one hundred and twenty-seven species 

 having been described. The members of the group differ in 

 size, color, and habits, and the individuals of the same species 

 show the very considerable amount of variation which seems 

 common to all those groups of animals which have been care- 

 fully studied. Happily the old notion that habits and instincts, 

 unlike structural peculiarities, are always uniform, is no longer 

 insisted upon, and there is ample evidence for the opinion that 

 functional variations are as common as morphological. We 

 have studied five species of this family and have found their re- 

 spective roles of great interest. 



According to Fabre the French members of this genus, al- 

 though they do not make their own nests, still exercise some 

 foresight in the matter by selecting a suitable crevice before 

 catching their prey. Among the species that we have studied 

 quinquenotatus, biguttatm, fuscipennis, marginatus, and in- 

 terruptus first catch the spider and then make the nest; while 

 calipterus and scelestus prepare the nest before capturing their 

 prey. 



