44 THE SOLITARY WASPS. 



five to thirty gnats. In some of them were cocoons, in others, 

 larvae, and in one, an egg. The gnats were very carefully ex- 

 amined, and all of them, from the cells that had been filled last 

 as well as from those provisioned earlier, were dead. 



Other species of Rliopalum are said to prey upon spiders and 

 aphides. 



Stigmus ainericanus Packard. 



Rliopalum was not the only wasp that had found a home in 

 the old stump. By dint of patient watching we discovered yet 

 other tiny black creatures going in and out of one of the little 

 holes. These wasps, which were scarcely more than one-eighth 

 of an inch in length, proved to belong to the species Stigmus 

 americanits, and we soon found that they were busily collecting 

 aphides which they probably took from the choke-cherry bushes 

 on the other side of the fence, since their journeys only occupied 

 three or four minutes. We could see that three wasj^s were 

 using the same gallery, all working together in peace and har- 

 mony. The hole aj)peared to be an old one, but whenever they 

 <3ame out they earned grains of pith, thus enlarging it to suit 

 their necessities. 



After having watched their goings and comings for several 

 hours we determined to open the nest. Following the tunnel 

 with some difiiculty for four inches we found a depression. In 

 this was a curious looking mass which proved, upon close ex- 

 amination, to be made up of grains of pith mixed with aphides. 

 To the ventral surface of one of these an egg was attached. 

 Half an inch further on was another depression holding a simi- 

 lar mass, the egg, in this case, ha-^ing been placed upon the dor- 

 sal surface. There were, in all, forty-five aphides, about equal- 

 ly divided between the two nests. We tested them very care- 

 fully and found that they were all dead. The gallery then, 

 must have been a general hall or passage-way used by several 

 individuals. We had seen three wasps and we found only two 

 nests, but probably we missed the third one amid the difficulties 

 of sawing and cutting. 



Hoping to rear the larvse we preserved the contents of both 



