THE GREEN JUNE BEETLE. 33 



hoppers, the function of mating and egg laying by the beetles might 

 continue normally in spite of their being parasitized. 



A Digger-wasp Enemy. 



Among the known natural enemies of the green June beetle, if we 

 except such birds as robins and blackbirds, is one that is more than 

 probably responsible for the extreme fluctuations in the numbers of 

 this species observed in some years and in certain localities. 



During the months of August and September of the last decade of 

 the nineteenth century, on numerous occasions the flight of a digger 

 wasp, Discolici dubia Say (fig. 6), was observed by the senior author. 

 The wasps gradually increased in numbers until they became suffi- 

 ciently abundant to attract general attention. The same abundance 



Fig. 6. — The digger wasp (DiscoJia dubia) : a, Female wasp ; 6, antenna of male ; c, cocoon 

 showing opening above. Twice natural size. 



was reported in other quarters in the city of Washington, and it 

 was presumed that white grubs of some sort were the attraction. 

 Finally it was learned that the insect seemed to be present only in 

 the male sex. Later the species was reared from Cotinis nitida in 

 different localities and reported to the Bureau of Entomology. 



In Maryland, near Washington, the same phenomenon was wit- 

 nessed, and it was also noted that the wasps congregated in great 

 numbers on convenient shrubbery. It may be said in general that 

 the wasp is most conspicuous on lawns and near shrubbery in just 

 such localities as are frequented by its host. One year this species 

 was so abundant in some of the smaller parks of Washington and so 

 disturbed the children who used the parks for playgrounds that the 

 wasp became the subject of newspaper notice. 



A few words in regard to the digger wasp above mentioned ma} r 

 be interesting. It is one of our medium-sized species, measuring 



186606°— 22— Bull. 891 3 



