154 AMERICAN HYMENOPTERA. 



Distribution. — This species has a wide range from Ottawa, 

 Canada, over the whole United States from Maine to Cali- 

 fornia and Florida, more or less of Mexico, Trinidad, and prob- 

 ably other of the West Indian Islands. 



Life history and habits. — This species, commonly known as 

 ** the long-tailed Ophion," and well represented in most col- 

 lections throughout the United States, is the largest Ameri- 

 can member of the genus. It is an active diurnal insect 

 rarely if ever attracted to light. Adults have been taken 

 from March 2 to October 18, but the majority appear during 

 April, May and June. The egg-laying habits and life history 

 have already been treated so far as known. It is often re- 

 ferred to as a parasite and frequently bred from the larger 

 saturnians and arctians. Eight or ten eggs are often laid 

 externally on a caterpillar, but as there is only food enough 

 for one, all but the strongest die in the struggle. As the 

 host spins a stout cocoon the larva of macrurus does not need 

 to look for further protection and spins up or sometimes 

 simply pupates within the cocoon of its host. The cocoon 

 when spun is tough, oval, about 32 mm. long by 17 mm. 

 broad, and occupies the greater part of that spun by the host. 

 The silk is fastened together by a dark secretion giving the 

 outside a dark brown color, but with a faint yellowish or 

 gold band around the middle. The interior is thinly lined 

 with a transparent substance giving a bright metallic luster. 

 The mature larva normally hibernates in the cocoon and the 

 adults usually emerge in the spring, but occasionally indi- 

 viduals appear in the autumn. 



Economic importance. — E. macriirus is without doubt the 

 most important member of this genus, being quite abundant 

 and always fatal to its host. Dr. Weed records an instance 

 were thirty out of fifty pupse of Samia cohunbia Sm. were 

 parasitized by this insect, and in another two-thirds the pupae 

 of Callosamia promethea were allEected, while Fiske and 

 Thompson report that it affected 32.7 per cent, of Prome- 

 thea, 7.3 per cent, of Cecropia and 10 per cent, of Poly- 

 phemus. Its value as a parasite is somewhat modified by 

 the fact already mentioned that " the larvae often fail to make 

 proper pupae, due probably to some disease which reaches 



