86 THE SOLITARY WASPS. 



with aphides, but in the cases that we observed they used 

 only spiders. There can be no mistake on this point as we more 

 than once took the spider from the wasp as she was entering the 

 nest. In a recent letter Mr. Ashmead says that his notes were 

 made, in the field, and that he probably mistook some closely 

 allied species for this one. 



We sometimes found the parasitic MelittoUa fly in the nests 

 of rubrocinctum, and from two nests we reared the common fly 

 Pachyophthalmus aurifrcms. 



We do not know how many nests are stored by the female in 

 one season, in any of the species of Trypoxylon. 



We are not as familiar with the habits of T. Udentatum as 

 with those of the other two, but we have a few notes relating 

 to the female. This little worker is the smallest of the three, 

 and like her sisters is a confirmed spider hunter. Once, when 

 out among the raspberry bushes, we had the good fortune to 

 witness a capture. The wasp seized the spider as it rested on a 

 leaf, by the top of the cephalothorax and, holding it firmly, 

 curved her abdomen under and stabbed the under face of the 

 cephalothorax. All her motions were deliberate, and after the 

 operation she delayed a moment before picking it up by a leg 

 and flying off. We often found raspberry stems which had 

 been filled with spiders by this wasp, but we do not know the 

 length of time required for the development of the egg nor how 

 long the larva eats before pupation. The cocoon is very dif- 

 ferent in appearance from those of rubrocinctum and albopilo- 

 sum, being excedingly long, slender, and almost white, instead 

 of short, wide, and brown. The perfect insects come out in 

 September and the last cocoon formed is the first one to hatch. 

 This was also true of the cocoons of rubrocinctum formed in 

 straws. The different habits of the hymenoptera in this respect 

 are very interesting. In the case of Ceratina dupla, the small 

 carpenter bee, the egg first laid hatches first, those above fol- 

 lowing in regular order. The lower ones wait patiently in their 

 cells until the one in the top cell has matured, when they all 

 come out at once. This is a very common species with us. Mr. 



