82 AMERICAN HYMENOPTERA. 



Abdomen strongly compressed, often darker at the apex; the two 

 basal segments long and slender, subtriangular, obliquely truncate, 

 acute posteriorly. 



This description has been prepared after an examination of 

 more than 300 specimens. 



Type. — Location unknown. 



This species is easily recognized by the two maculae and 

 often a line, in the discocubital cell, and by the light color of 

 the body. E. arcuatus is so closely related to purgatus that it 

 can only be considered as a subspecies. It is usually notice- 

 ably larger, the larger macula always appendiculate and the 

 bulla of the discocubital vein distant one-half the width of 

 the discocubital cell from its apex, while in ptirgahis it is 

 scarcely one-fourth the width from the apex. 



Distribution. — This species ranges from the Boreal Zone in 

 southern Alaska (50° lat. ) to the Tropical Zone in Mexico (26° 

 lat.), and the West Indies to Chili in South America. I have 

 before me specimens from Fox Point, Alaska* ; Washing- 

 ton ; Mt. Hood, Oregon: Santa Cruz Mountains, etc., Cali- 

 fornia ; Mexico ; Chili ; Pinar del Rio, Cuba ; Jamaica ; 

 Brownsville, Texas ; Louisiana; Alabama; Florida; Penn- 

 sylvania ; Illinois ; Colorado ; Montana ; New Hampshire ; 

 Grand Lake, Newfoundland ; Winnipeg, etc., Canada. Speci- 

 mens from many intervening places show that it ranges over 

 most of Canada, all of the United States, south into Mexico, 

 Central America, part at least of the West Indies, and Chili 

 in South America. 



This wide distribution led me to expect to find two species, 

 but after careful study I have not succeeded. 



Life history. — This is the member of the genus most fre- 

 quently taken in the United States while collecting in the 

 daytime, and the one most common in collections. The 

 adults fly in Massachusetts from the last of May till the last 

 of September, and farther south occasionally from March to 

 December. They are diurnal and probably crepuscular in 

 habit since they are attracted to light to a certain extent. 



* " An Indian village at the extreme southeastern corner of the Alaska 

 mainland, July 26." 



