THE STATE ENTOMOLOGIST. 



103 



gaster (Fig. 23) which preys upon the Army-worm. It differs also 

 from most other insects of the same genus, by each individual larva 

 as it eats through the skin of the Canker-worm, spinning its pale 

 greenish-white cocoon alone, and not in company. About ten per 

 cent, of the worms which I have endeavored to breed, have been de- 

 stroyed by this parasite. Harris mentions the larva of another four- 

 winged fly, and that of a two-winged fly belonging to the genus Ta- 

 china, which also infest the worm, destroying about one- third of them 

 in Massachusetts. There is also a very minute and undescribed spe- 

 cies of Platygaster which pierces the egg of the Canker-worm, and 

 drops one of her own into it, from which in due time the perfect fly 

 develops. 



Among the Cannibal insects, which prey upon it, may be men- 

 tioned the Ground-beetles, two of which I have found preying upon 

 this worm, namely, the Rummaging Ground-beetle ( Calosoma scruta- 

 [ Fi s- 69 -l tor, Fabr. Fig. 69), a large and beautiful 



insect, with the wing- [Fig. 70.] 



covers golden-green, and 

 the rest of the body 

 marked with violet-blue, 

 gold, green, and copper; 

 and the Fiery Ground- 

 beetle (Calosoma cali- 

 dum, Fabr. Fig. 70.), a 

 black species of almost 

 equal size, with copper 

 colored spots on the wing- 

 covers. These beetles are very active, and run over the ground in 

 search of soft-bodied worms, and will even mount upon the trunks of 

 trees for the same purpose. 



The Fraternal Potter- wasp (Eumenes fratema, Say), is stated by 



Harris, to store her cells with Can- 

 ker-worms, often gathering eighteen 

 s or twenty of them for a single cell. 

 This wasp (Fig. 71, a), is quite com- 

 mon in St. Louis county, and uses 

 other species besides Canker-worms 

 as food for its young. Its clay nest 

 (Fig. 71 5, entire; c, the same cut 

 open shortly alter it was built, show- 

 ing the manner in which it is com- 

 pactly crowded with green worms), may often be found attached to 

 the stems of the Goldenrod and of other plants in the open air, or 

 cemented under the loose bark of some tree. It has even been found 

 attached to the leaves of a deciduous plant, where it must neces- 

 sarily fall to the ground in winter and lie there till the perfect insect 

 issues in the following summer. 



