451 THE BLriTEKFLIES OF NENV EX(iLANI). 



lite may not becumo extinct fur several days. At other times from sonic 

 movement of the caterpillar they become merged into one mass. One sncli 

 cluster was formed of regular layers of cocoons piled like so many logs upon 

 one another, with no loss of space between them, so that they were compact 

 and unyielding, the ends of the cocoons or sides of the mass, and espec- 

 ially one side, furnished with a quantity of loose, iiocculent matter, together 

 forming a well-rounded, short-oval mass, 11 mm. long, 7 mm. broad and 

 4 nun. high, the breadth being the direction of any one cocoon ; without 

 the iiocculent matter it would have been but 5 mm. broad. The cocoons 

 are made of thicker or more compacted silk than the rest, and all parts but 

 the extremity where the head of the future pupa is to lie are completed 

 first, and then this end is sealed up with a thin, nearly flat covering, easy 

 or the jaws of the imago to sever. The cocoons are cylindrical, of uniforui 

 size, o mm. long and .65 mm. broad, and are not so thick as not to show 

 the dusky color of the enclosed pupa. Even in the very regular mass I 

 have desci'ibed, the anterior extremities of the cocoons were not all placed 

 in the same way, but directed indifferently toward either side. In the 

 different instances in which I counted them, the cocoons from a single 

 caterpillar varied from twenty-six to thirty-nine in number. 



The grubs emerge from the caterpillars in the early })art of June and 

 appear as winged insects in about eight or ten days. A second brood 

 emerges in the middle of July, and a third, which a[)pcars in September, 

 remains in the cocoon all winter. 



In emerging from the cocoon, the little hypmenopteron, Apanteles ata- 

 lantae, cuts away the thin circular lid and pushes it upward, where it 

 remains entangled in the threads of the Hocculent mass. The males are 

 the least abundant : in one instance I ol)tained seven males and twenty- 

 two females : in another six males and twenty-nine females. The males 

 make their appearance first, although the whole comnumity emerges within 

 an hour's time, with the occasional exception of a straggler who may be 

 detained a day or more. The moment they have cut their way out they 

 race about with widely outstretched jaws, their antennae trembling 

 vigorously. 



To see the operation of this little parasite I placed some females two 

 days old under ji glass with caterpillars of atalanta, some fully grown and 

 others about half as long. The parasites were put in first and the cater- 

 pillars introduced afterwards. There was no change in the action of the 

 parasites at this time, no recognition of the presence of their victims, 

 although both before and afterwards thev were in constant motion, evi- 

 dently in search of prey. In their blind wanderings, coming into con- 

 tact with a bit of web made by a lar\a of atalanta in the angle of a nettle 

 leaf and vainly endeavoring t<» penetrate it, they at once went vigorously 

 at work to bite their way throutjli, as if confident that the object of their 



