— 148— 



Rhogas fumipennis, Cresson. 



This insect was described (Trans. Am. Ent. Soc. , Vol. 11, p. 378) 

 in 1869 by Mr. E. T. Cresson from a specimen (9) collected in Illi- 

 nois, and I believe, has not since been especially mentioned in our 

 literature, so that its host is now first reported. 



The only other North American species of Rhogas whose life- 

 histories have been obser\'ed so far as known to me are [i] the par- 

 asiticus of Norton (Trans. Am. Ent. Soc, Vol. II, p. 327), and [2] the 

 rileyi of Cresson (Ibid, p. 383). The former was bred from Lophyrus 

 abietis, Ham, by its describer ; and the latter from Acronycfa oblinita, 

 Sm. & Abb., by Dr. Riley (Third Kept. St. Ent. Mo., p. 71). The 

 breeding of a Rhogas from a tenthredinid is exceptional, and though it 

 has twice been reported in Europe, — once by S. V. Vollenhoven, who 

 bred R. circumscriptus, Nees, from a Lophyrus cocoon, and again by 

 Brischke, who mentions the breeding of a Rhogas from a Nemalus co- 

 coon, — the fact has commonly been discredited by* European Entomo- 

 logists (Marshall, Monograph of Brit. Braconidae, Trans. Ent. Soc. 

 Lond., 1885, Pt. I, p. 87). This additional testimony however by so 

 reliable an observer as Norton renders it almost certain that some spe- 

 cies attack Hymenopterous larvae. 



But the normal habit of this interesting genus is to attack young 

 Lepidopterous larvae and kill them before they are ready to become 

 pupae. Marshall remarks: "The insects of this genus manifest a 

 peculiar economy. They are solitary parasites of young lepidopterous 

 larvce, the bodies of which they do quit at the time of pupation, but 

 make their cocoons inside protected by the indurated skins of their 

 victims. The perfect Rhogas ultimately escapes through a hole bored 

 in the posterior dorsal segments of the caterpillar." And Dr. Riley says 

 that i?. rileyi causes "the larva of the Smeared Dagger to die when 

 about full grown, and its contracted and hardened skin, which may 

 often be seen dunng the winter with its head attached fastened to the 

 twigs of apple and willow trees, forms a snug little house, where the 

 parasite undergoes its transformations, and through which it gnaws a 

 round hole to escape the latter part of April." 



The habits of Rhogas fumipennis correspond very well with those 

 of the species just mentioned. The dead Hemaris larvae may be found 

 attached to the twigs of their host plant greatly shriveled, and with the 

 skin hard and dry. Inside of this is the Rhogas pupa, and when the 

 insect is ready to emerge it gnaws a circular opening, about two mm. 

 in diameter, in the posterior dorsal segments and comes forth. I judge 

 that the time spent in the pupa state is about a fortnight. Our specimens 



