208 NATURE SKETCHES IN TEMPERATE AMERICA 



irregularly arranged around the back portion. These little 

 protuberances are fashioned when the clay is soft. 



I once saw three nests of this interesting wasp on a twig of 

 a beech tree. They were compactly built in a row, firmly 

 saddled on the beech twig, the middle one =belng closely wedged 

 and cemented between the other two. All the openings of the 

 jugs were perfectly sealed with smoothed-off mud. Probably 

 all of the nests were made by the same mother insect. After 

 keeping the nests indoors for six days, I found two of the slender- 

 waisted wasps on the windows inside our house. This was the 

 first intimation that the jug-makers had made their exit from 

 their confined cells. Sure enough, an examination of the nests 

 revealed that all three of the occupants had gone. They had 

 not, however, pushed out the little plugs in departing, but 

 instead, each one of the nests presented a little hole in the side, 

 of ample size, through which the wasp's body could pass. It 

 would appear from these holes that the wasps had gnawed their 

 way out with their powerful mandibles-. Gibson relates in 

 "Sharp Eyes" that the plug to the jug is pushed out by the 

 chrysalis when it appears as a full-grown wasp. But the 

 writer's observations, as shown above, do not coincide with 

 this view, for all the wasps kept under observation broke out 

 through the side of the nest. 



The mason-wasps are rather small in size and are identified 

 by the characteristic form of the abdomen. The latter is 

 attached to the thorax by a slender peduncle, which is slightly 

 swollen backwards. The next segment of the abdomen adjoin- 

 ing the peduncle is globular, the remaining ones forming a 

 tapering point. Again Gibson writes that when this wasp 

 completes her jug-nest, "The wasp lays an egg within it, and 

 then proceeds to pack it full of tiny green caterpillars, each of 

 which she has paralyzed but not killed, by a stab of her sting. 

 The opening to the vase is then plugged up with a mud cork. 

 Presently the egg hatches into a little grub, that feeds for 

 the rest of its days on the living store of food." There are 

 doubtless individual differences in the habits of the jug-maker, 

 and much is to be learned about them by painstaking observa- 

 tions. It is well to mention here that Walsh reared a parasite 

 Chrysis caerulans from the cells of this potter wasp, and it 



