THE LITTLE FLYCATCHER. 75 



probable, the work was done that morning, the task must have 

 been begun at a very early hour. 



The egg, which was laid just before nine o'clock on the morn- 

 ing of August seventh, hatched at a little after nine on the 

 morning of August eighth. The larva began to eat at once and 

 devoured all the inside of the thorax and abdomen of the fly 

 to which it was attached, in the first twenty-four hours. On 

 August twelfth it had reached the sixth fly, and we supplied it 

 with three more. On August fourteenth these were gone and 

 we again replenished its larder, this time with two flies. The 

 larva had partly eaten these when something went wrong. Its 

 appetite failed, and on August sixteenth it died. 



We find but meagre notes on the genus Oxybelus. Ashmead 

 says that no observations have been made on the American 

 species but that in Europe they are found to burrow in sand 

 and to provision their nests with dipterous insects. He also 

 says that according to Yerhoeff the species in this genus do not 

 paralyze their prey by stinging as they are unable to do so on 

 account of the rigidity of the abdomen, but that instead, they 

 -crush the thorax with the mandibles just beneath the wings, 

 the centre of the nervous ganglia. He found in one nest a 

 dozen flies (Hydrotaca) and all had the thorax crushed and 

 were dead. In the case of our wasp we do not know how the 

 flies were killed but there was no crushing of the thorax. The 

 larva devoured, in all, ten flies. At the time of its death it had 

 probably finished the larval stage of its existence since nine 

 days had elapsed since the hatching of the egg. It may be that 

 this period just before pupation is a critical point in the life 

 history of a wasp. We lost several of our nurslings at this time, 

 and Fabre has noted that when, on account of the presence of 

 parasites, the larva of Bembex rostrata had lacked something 

 of its usual amount of nourishment, it perished miserably at the 

 end of its larval stage, not having strength enough to spin its 

 cocoon. ISTo waspling in our charge ever died from lack of nour- 

 ishment on that score our consciences are clear; but it was 



