SOME FOSSIL INSECTS FROM FLORISSANT, COLORADO. 



By T. D. A. COCKERELL, 

 Of the University of Colorado, Boulder. 



The new species described below are in the collection of the United 

 States National Museum. The three Hymenoptera are sawflies, 

 bringing the total of Florissant fossil sawflies up to 42. The new 

 Plecia brings the list of Florissant Bibionidse to six, and the Dioctria 

 is the thirteenth fossil Asilid from that locality. None of the genera 

 are new to Florissant. 



HYMENOPTERA. 



TENTHREDELLA OBLITA, new speciei. 



Length, about 12 mm.; width of head, 3 mm.; length of anterior 

 wing, about 11 mm.; head, thorax, and antennae, black; abdomen, 

 dark, with the sutures pallid; wings, slightly dusky; nervures, fus- 

 cous. Venation normal for the genus; interradial vein strongly 

 arched (much more so than in T. saxorum) ; second cubital cell long, 

 receiving first recurrent vein near its middle; third cubital cell about 

 twice as broad on apical side as on basal; lanceolate (anal) cell con- 

 tracted, at the narrowest part a straight cross-nervure. In the hind 

 wing the anal cell is broadly truncate, not at all petiolate, at the 

 end. 



The following measurements are in microns: First radial cell on 

 third cubital, 832 (1136 in T. saxorum) ; second radial on third cubi- 

 tal, 336 (192 in T. saxorum) ; second cubital on first discoidal, 704 

 (560 in T. saxorum) ; second cubital on second (third, of authors,) 

 discoidal, 736 (800 in T. saxorum) ; first discoidal on submedian, 336 

 (352 in T. saxorum) ; length of cross-vein of anal, about IGO; width 

 (depth) of anal at level of end of submedian cell, 480. The basal and 

 first recurrent veins are parallel. Most nearly allied to T. saxorum 

 Rohwer, but distinct by the quite different pattern of the abdomen 

 and the details of the venation. Also allied to T, avia Brues, but the 

 color-pattern is quite different, the veins are dark, and the anal cell is 

 contracted at the cross-vein. T. saxorum has the apical part of the 

 abdomen black, as in the living Allantus unicinctus Norton; while 



Proceedings U. S. National Museum, Vol. 63-2210. 



889 



