26 Some Solitary Wasps of Texas. 



closes her nest before leaving it, often smoothing it over with consid- 

 erable care. In this way she is spared the inroads that commensal- 

 istic larvae make into Bemhexs store of food. 



In their semi-social habit Bembex (and this would apply to ilft- 

 crobembex) has been regarded as transitional between the truly soli- 

 tary and the social wasps. Both genera are more solitary than social 

 for their only social trait consists in a tolerance of each other's pres- 

 ence in the immediate neighborhood. Beyond an occasional quarrel 

 or the stealing of each other's flies the wasps preserve the peace of 

 the colonies. This recalls by way of contrast the fierce combat of 

 two Ammophilae which happened to dig their nests near each other. 

 Bembex is furthermore said to show a social trait in the co-operation 

 of the individuals in driving away parasitic flies. This is, however, 

 more imaginary than real, for the fly is not killed nor is it driven 

 away from the colony but merely from one individual's nest to an- 

 other's. 



Both Bembex and Microbembex are common species throughout 

 the sandy woods. Every path or road or other area devoid of vege- 

 tation is occupied by individuals of these flourishing species. If an 

 open spot is a favorable nesting place, wasps may congregate there 

 in numbers sufficient to riddle the surface with holes, thus forming 

 an extensive colony. Now, since such spots are not common, the 

 thought suggested itself that the very numbers of the wasps forced 

 them to occupy the same patch of ground, to dig their nests side by 

 side, and thus by virtue of their familiarity with one another to 

 live together in comparative peace. The tolerance of one another's 

 presence would then be the first trace of the social instinct. The 

 fact that the two different genera live together as peacefully as does 

 Bembex with Microbembex seems to point to the same conclusion. 

 Moreover, neither genus seems to show a marked predilection for 

 living in the colony, for isolated individuals of both will be found 

 throughout the woods, evidently as happy as when joining in the 

 busy hum of a colony in the noon-day sun. 



. May it not even be that in this way numbers was the first stimulus 

 toward social life as shown by a trace of it in Bembex and Microbem' 

 bex? 



