30 DEPARTMENT BULLETIN 126*7, U; S. DEPT. OP AGRICULTURE 



of a robber-fly (Erase lateralis Macq.) as an enemy to this and other 

 scarabaeids. At Tappahannock the junior writer observed the larva 

 of a similar or closely related form preying upon larvae and pupae 

 of a species of Phyllophaga, but never found it attacking those of 

 E. rugiceps. Ants were found to attack and kill any larvae of the 

 latter or of other scarabaeids that chanced to be exposed on the 

 surface, and it is reasonable to suppose that they would do the same 

 thing underground, an inference which is supported by the observa- 

 tion that rarely, if ever, were scarabaeid larvae of any kind en- 

 countered in the vu lity of ant colonies. 



In the junior writer's experience the most frequent enemies are 

 certain mites which attach themselves to the body surface. That 

 these mites derive any nourishment from their host the writers are 

 not prepared to assert. Nathan Banks, then of the Bureau of Ento- 

 mology, to whom specimens of the mites were sent and who deter- 

 mined them as the hypopus stage of Rhizoglyphus phylloxeras Riley, 

 asserts that they are saprophytes, feeding upon decaying vegetable 

 matter. Whatever may be the normal feeding habits of the mites, 

 it is the experience of the writers as well as of other investigators 

 (Davis, 5; Smyth, 12) that the presence of these and other mites is 

 highly detrimental to the grubs and also to the pupae. Upon adults 

 they appear to have little effect. The junior writer has observed 

 adults almost literally encrusted with mites and apparently none the 

 worse for the presence of their uninvited guests. Larvse and pupae 

 are more susceptible, however, and it is the opinion of the writers 

 that the high mortality in the larvae and pupae in the breeding cages 

 and boxes was due in large measure to the mites. Larvae have been 

 found in the field with the mites attached to them, so that it is not 

 alone in the breeding boxes that they are attacked. 



At Tappahannock in the summer of 1915 these mites were very 

 numerous and troublesome, but in the following year they had all 

 but disappeared. Possibly such fluctuations in the numbers of the 

 mites from year to year may be one of the factors in determining 

 the rather sporadic and irregular manner in which destructive out- 

 breaks of E. rugiceps appear to occur. 



The larvae and pupae were found occasionally to be infested with 

 minute whitish nematode worms. Usually these were observed on 

 the surface, where they tended to congregate in the intersegmental 

 furrows, but sometimes an identical or closely similar type of nema- 

 tode could be seen, through the transparent body wall, moving about 

 in the body fluid. 



There are unquestionably two species of true parasites, one of 

 which, a dexiid fly, W. R. Walton determined as Megapariopsis 

 opaca Coq. The maggot of this fly feeds within the body of the 

 larva until it is ready to form the puparium. Those reared by the 

 writers bored their way out of the host shortly before changing to 

 puparia. 



The other parasite was a hymenopterous insect, of which none was 

 reared to the adult stage. For this reason the specific identity of 

 the parasite was not determined, but it closely resembles Tiphia 

 inornata Say, the best known probably of all the enemies of Phyllo- 

 phaga as described by Davis (|, p. IS) and Smyth (12). The young 

 of this parasite is a thick white maggot, which during the time it 

 is feeding lies in a transverse position on the dorsum of its host 



