THE WOOD-BORERS. 87 



Comstock says that, so far as lie knows, dupla is the only solitary 

 bee that watches over her young until they become mature. In 

 the case of some of the cuckoo-flies (Chrysididae), we have ob- 

 served that the e^g laid first hatches first, but that the mature 

 insect, instead of waiting for the way to be clear, gnaws a hole 

 through the side of the stem, and thus makes its entrance into 

 the world. 



Years ago, when we found that many of the Epeiridae laid 

 enormous numbers of eggs (A. cophinaria from 500 to 2000), 

 we wondered what became of the thousands of spiderlings. An 

 acquaintance with Trypoxylon has shown us their fate, and has 

 given us an illustration of how closely the two groups are re- 

 lated. To make a very modest estimate there must have been 

 twenty wasps at work in our straw-stack. During the six weeks 

 which make the busiest part of their working season each of 

 these must have stored, at the very least, thirty cells, putting an 

 average of ten spiders into a cell. It may then be considered 

 certain that the straw-stack, with its working surface of 12x20 

 ft., was the mausoleum of six thousand spiders, and it is very 

 probable that twice as many were interred within its depths. It 

 must be remembered, too, that before the spiders have grown 

 large enough to be interesting to rubrocinctum, bidentatum has 

 had her turn at them, and that those that are allowed to grow 

 too large for rubrocinctum, are preyed upon grade after grade, 

 first by albopilosum and finally by Pelopaeus, Pompilus, and 

 other genera. 



The wasps of this genus lose their interest in family affairs 

 after the second week in August, though after this time they 

 may still be seen taking their well-earned holiday on the blos- 

 soms of the aster and the golden-rod. 



