THE DIODONTI. 103 



bent all our energies upon keeping tliem in view — in vain. They 

 rose upon their wings, and disappeared. Baffled again and 

 again, we called the children of the household to our aid and 

 offered prizes for the discovery of the nests, and these recruits, 

 thinking that perhaps the wasps crossed the garden to the barn- 

 yard, searched that enclosure thoroughly, and found in the straw- 

 stack, nests indeed, hundreds of them, only they belonged to 

 Trypoxylon. Not discouraged, our energetic assistants next 

 scrambled over the fence to the north, invading the woods, and 

 there in a worm-eaten weather-beaten stump they found more 

 nests — but they belonged to Rhopalum and Stigmiis. Three 

 days passed before we dropped our eyes to the ground at our 

 feet and found that there, close by, were the abiding places of 

 Diodontiis. 



From the outside the nests show a tiny hole with some grains 

 of dirt irregularly heaped around the edges. We had the great- 

 est difficulty in excavating them, as the crumbling earth fell into 

 the narrow gallery at every touch, making it almost impossible 

 to trace. The nest that is shown in the drawing had been 

 started in a small lump of earth which lay on the ground, and 

 this made it easier to follow the entrance tunnel. (PL X., 

 •fig. 5.) 



It takes the wasp about an hour to dig her nest. She carries 

 the earth out with her mandibles and first legs, backing from 

 the hole. The gallery runs in obliquely and ends in a pocket 

 to one side. The nest is not closed until the provisioning is 

 completed . 



When an aphis is brought home the wasp remains within the 

 nest only a few moments and then is off in search of another. 

 The egg is not laid on the first one brought in since it is often 

 lacking in nests which contain six or eight aphides. If the 

 weather is hot and sunny it is not unusual for a nest to be made 

 and completely provisioned on the same day, but when it is cool 

 or cloudy americanus works very slowly or not at all. About 

 forty aphides are necessary for the provisioning of a single nest. 



On the same bushes with these wasps we constantly saw a 



