II 



WASPS EUMENIDAE 



observations on 0. rcniformis. This Insect provisions its crli 

 with small caterpillars to the number of twenty or upwards (Fig. 

 28, A.) The egg is deposited before the nest is stocked with food ; 

 it is suspended in such a manner that the suspensory thread 

 allows the egg to reach well down towards the bottom of the 

 cell. The caterpillars placed as food in the nest are all curled 

 up, each forming a ring approximately adapted to the calibre of 

 the cell. Fabre believes these caterpillars to be partly stupefied 

 by stinging, but the act has not been observed either by himself, 

 Keaumur, or Dufour. The first caterpillar is eaten by the wasp- 

 larva from its point of suspension ; after this first meal has been 

 made the larva is supposed to undergo a change of skin ; it then 



FIG. 30. Odyncrus antilope ?. Britain. 



abandons the assistance of the suspensory thread, taking up ;i 

 position in the vacant chamber at the end of the cell and draw- 

 ing the caterpillars to itself one by one. This arrangement 

 permits the caterpillars to be consumed in the order in which 

 they were placed in the cell, so that the one that is weakest on 

 account of its longer period of starvation is first devoured. 

 K.ibre thinks all the above points are essential to the successful 

 development of this wasp-larva, the suspension protecting the egg 

 and the young larva from destruction by pressure or movement 

 of the caterpillars, while the position of the larva when it leaves 

 the thread and takes its place on the floor of the cell ensures its 

 consuming the food in the order of introduction ; besides this the 

 caterpillars used are of a proper size and of a species the 



