BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [40] 



conidse. The Ghrysididse and certain other less important families are 

 also parasitic, but are more easily obtained by general collecting. The 

 implements necessary for collecting Hymenoptera are the sweeping-net 

 and the beating-net. Many rare forms of the smaller parasitic families 

 may be obtained by sweeping the grass and foliage of all sorts. The 



C 



Pig. 60. — A Saw-fly {Nematus ventralis) . a, a, a, young larvic; &, fuUgrowii larva ; c, cocoon; d, adult; 



all slightly enlarged. 



Proctotrypidse may be collected in quantity by sifting leaves and rub- 

 bish collected in the woods. Mr. William H. Ashmead, who has made 

 an esiDecial study of this group, finds winter sifting x3rofitable. Dried 

 leaves and rubbish are sifted, the finer portion being retained and 

 transferred to a bag. When a sufficient quantity is collected it is re- 

 moved to a warm room. Many hibernating species are taken in this way^ 

 and, revived by the warmth, are easily noticed when the material is 

 spread on white paper. 



On account of the interest attaching to a knowledge of the various- 

 hosts of parasitic insects the collector should always aim to obtain the 

 latter by breeding as much as possible. This can easily be done by 

 keeping a lookout for larvae of all sorts which give evidence of being j)ar- 

 asitized. The larvse of Lepidoptera found late in the fall are very apt to 

 be parasitized, and should be collected and kept over the winter. The 

 parasites will emerge throughout the winter season and in the early 

 spring. Such larvfe will be found on the trunks of trees, in the crevices 

 of the bark, and the cocoons of parasites will also be found in similar 

 situations. 



