INSECTS AFFECTING PARK AND WOODLAND TREES 



'39 



more general in the vicinity of tlie grounds of the- Department of Agricul- 

 ture, where most of the observations were made, than in other portions of 

 the city. The difference due to locality is also shown by the parasites' in 

 the state collection reared by the late Dr Lintner from this species, though 

 his study of them was by no means so extensive as that at Washington. 

 The one occurring most abundantly was Tachina mella Walk. 

 Pimpla hirticauda Prov., a species not reared at W^ashington from 

 this insect, was bred in greater numbers than any other of the larger 

 hymenopterous parasites. Most of the individuals belonging to this species 

 were reared in July, but two appearing in June and a few others in August. 



Fig. 21 Dibrachys boucheanus 

 </=head of larva: ^—antenna of adult 

 Div. Ent. Tech. Ser. 5. 1897) 



a; ^=pupa; t=adult female — greatly enlarged; 

 jre enlarged, (.\fter Howard, U. S. Dep't .\gric. 



Pimpla inquisitor Sa)', P. c o n q u i s i t o r Say and P. a n n u 1 i p e s 

 BruUe occurred in about equal numbers. Of the smaller primary parasites 

 Ptero mains cuproideus How. and an unnamed species belonging to 

 the same genus were about equally abundant. 



Though the list of primary parasites is long and includes some very 

 important species, many of these are in turn the victims of enemies. The 

 parasites breeding in those which prey on injurious forms must be classed 

 as enemies to man, since they indirectly protect a species injurious to his 

 interests by destroying large numbers of its parasites. One of the most 



'Determined tlirough the courtesy of Dr L. O. Howard. 



