428 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



Washington; Meyers Vade (F. B. Herbert), Yosemite (J. J. Sullivan), 

 California; Xanana, Alaska (K. W. Strangman); Pisgah Mountain, 

 North Carolina, altitude 5,600 feet (A. D. Hopkins). 



Host. — A. B. Champlain of the Branch of Forest Insects has 

 reared this species from the larva of a species of Xeris living in 

 Abies concolor. 



MEGARHYSSA ATRATA (Fabricius). 



Ichneumon atratus Fabricius, Spec. Insect, vol. 1, 1781, p. 436. 



Ichneumon tenehrator Thunberg, Bull. acad. sci. St. Peters., vol. 8, 1822, p. 260. 



Ehyssa laevigata Brull^, Hist. Nat. Ins. Hym., vol. 4, 1846, p. 78, pi. 40, fig. 2. 



Types of none of these species have been seen. Discussion based 

 on specimens from the localities listed below. 



Distribution. — Billerica, Massachusetts (T. F. Lyon) ; Long Island, 

 New York; Cory (W. R. Walton), Harrisburg (W. S. Fisher), Guys 

 Mills (Heinrich), Pennsylvania; Washington, District of Columbia; 

 Great Falls, Virginia (R. P. Currie) ; Cabin John, Plummer's Island 

 (H, S. Barber) Maryland; Chattanooga, Tennessee; East Florida 

 (Ashmead); BeUevue, Indiana; Georgia (J. H. Bryan); Clinton, 

 Arkansas. 



Although this species is common there seems to be no positive 

 record of its having been associated with its host. 



UNRECOGNIZED SPECIES. 



THALESSA7 HISTRIO Kreichbaumer. 



Thalessa? histrio Kreichbaumer, Ann. naturhist. Hofmus. Wien., vol. 5, 1890, 

 p. 487. 



It is certain that this species does not belong to the genus Megarhyssa 

 and although Moscary places it in the genus SpirJiyssa the writer 

 is of the opinion that when the type is examined it will be found to 

 belong to some other tribe. 



Tribe XOEINDINI Cushman and Bohwer. 

 Xoridini Cushman andRonwER, Proc. U.S.Nat.Mus., vol. 57, 1920, p. 395. 



As here defined the tribe Xoridini contains only those genera 

 which have the mandibles edentate apically so it is only a part of 

 the tribe Xoridini of other authors. 



In certain characters the Xoridini are allied to the Rhyssini, 

 while in others they are allied to the Odontomerini. The apically 

 edentate mandibles will, however, easily distinguish this tribe from 

 all others of the subfamily. 



As far as known, all of the species are parasitic on the larvae of 

 insects living in wood. 



Tribal characters. — Head subquadrate, not swollen below the 

 antennae, posterior orbits broad; mandibles edentate apically 

 and usually without an inner tooth, occasionally (Poemenia) with a 



