1909.] PUBLIC DOCUMENT- -No. 73. 63 



in habit during its early stages, is of considerable importance as 

 an enemy of the brown-tail moth abroad, and likely to become so 

 here. 



The Hymenopterous parasites of the gypsy and brown-tail 

 moths, while less numerous than the Dipterous, include several 

 very important species very diverse in their habits. These in- 

 sects are more adaptable to increase in the laboratory than are 

 the Dipterous; and one in particular, which attacks the hi- 

 bernating brown-tail caterpillars within their nest, has been 

 reared in the laboratory by the hundreds of thousands, and at 

 small expense. There are on hand at the present time, await- 

 ing the proper time for their liberation, in excess of half a mil- 

 lion of the young of this insect, the result of the increase from a 

 few thousand which were kept on hand during the summer. 



Another species, Monodontomerus, which attacks the freshly 

 formed pupse of the gypsy and brown-tail moths, and which hi- 

 bernates as an adult within the winter nests of the last-named 

 species, has shown a rate of increase and of spread under natural 

 conditions in Massachusetts which is almost incredible. It has 

 been secured from brown-tail moth nests in no less than six 

 different and widely separated towns this winter, and, while the 

 numbers present in each instance were small, the wide dissem- 

 ination of this parasite means that an astonishing number are 

 present in the aggregate. 



One of the features of the work for 1908 was the rearing and 

 liberating of more than 12,000 of a small species of Apanteles 

 which attacks the brown-tail caterpillars in the fall, before they 

 have entered their hibernating webs. The young parasite lives 

 within these caterpillars, without causing them inconvenience, 

 until after they have emerged from their webs and have fed 

 for a period in the spring. At about the time when the healthy 

 caterpillars pass their first spring molt the parasitized indi- 

 viduals die, and the parasite larva emerges and spins a cocoon 

 similar in appearance to that of the Japanese parasite, but, 

 unlike that species, always solitary. The handling and feeding 

 of large numbers of caterpillars necessary to produce 12,000 of 

 these adult parasites by means of any of the appliances for 

 this purpose ordinarily in use in entomological laboratories was 

 wholly impracticable, and made imperative some new device. 



