118 NEW YORK STATE MUSEUM 



A glance at the above table will show that this insect has a well 

 defined period of flight, and one that does not overlap the time 

 O. b i 1 i n e a t n m is abroad, except in the case of scattering 

 individuals. This species appears early in Mav, is most abund- 

 ant the latter part of the month, and occurs somewhat rarely 

 during June with belated individuals in July, August and Sep- 

 tember, while O. bilineatum does not occur till August and 

 then only in scattering numbers till the latter part of the month. 

 This marked difference in the time of flight between these two 

 parasites indicates that either they are two broods of the same 

 insect or else that they are distinct species. The structural differ- 

 ence to be described later must be regarded as proofs of their 

 distinctness. The large eyes and many individuals taken in the 

 trap lantern indicate a crepuscular or nocturnal habit. 



Hosts. This parasite has been reared from E p a r g y reus 

 t i 1 3' r u s Fabr. Prof. G. C. Davis, when at the Michigan Agri- 

 cultural College Experiment Station, wrote us that he had bred 

 the insect repeatedly from H a 1 i s i d o t a c a r y a e Harris and 

 S y m m e r i s t a a 1 b i f r o n s Abb. & Sm. It is probably para- 

 sitic on a number of other related insects. 



Description. Ferruginous or fulvo-ferruginous with frequently 

 a decidedly fulvous tinge on the thorax, which latter is shorter 

 and the abdomen considerably shorter than inO. bilineatus. 



Face ferruginous, or laterally fulvous; head medium; mandibles 

 bidentate, tipped with dark brown, clypeal fossae deep, antennae 

 usually longer than the body ; the fossae at their bases not deep ; 

 eyes large, reaching nearly to the base of the mandibles. Ocelli 

 black, nearly contiguous and the posterior close to the eyes. 

 Thorax short, ferruginous or fulvo-ferruginous; mesothorax con- 

 vex; scutellum and postscutellum prominent; metathorax usually 

 with very prominent carinae inclosing deep, four sided areas, and 

 the pedicel of the abdomen surrounded by a high carina. Wings 

 hyaline; cubitodiscoidal nervure strongly appendiculate. First 

 recurrent nervure only about one third the length of the second; 

 bulla of the latter close to the cubitodiscoidal nervure, and that 

 of the latter nearer the second discoidal nervure than the appen- 

 dix. Legs long, fulvo-f eri^iiginous ; abdomen much shorter than in 

 O. bilineatus, very strongly compressed and the posterior 

 segments usually darker in color. Clasps of male subtriangular, 

 obtusely rounded, length 14 mm, wing spread 26 to 30 mm. De- 

 scribed from numerous specimens of both sexes. 



