240 BRITISH GUIANA TIPULIDAE 



This is the third American Orimarga to be described and it is 

 easily distinguished from the related species in this genus, and in 

 Diotrepha, by its spotted wings. 



Genus DIOTREPHA Osten Sacken 

 1878. Diotrepha Osten Sacken, Cat. Dipt. N. Am., ed. 2, 27 and 219. 



Diotrepha atribasis sp. n. 



Large species (length 8 to 10 mm.); the femora and tibiae tipped with 

 black and the base of the tibiae black; tip of Ri obliterated. 



Male. — Length, 9 mm. ; wing, 5.5 mm. 



Female. — Length, 8 to 9.8 mm.; wing 5 to 6.3 mm. 



Male. — Rostrum and palpi dark brownish black. Antennae with the elon- 

 gated basal segment and the second globular segment dark brownish 

 black ; flagellum much paler brown, in some specimens almost white. Head 

 light brown with a grayish bloom, very pale on the front and anterior por- 

 tions of the vertex. 



Thoracic dorsum light brownish gray. Dorsal pleurites a little grayish, 

 the ventral pleurites and the sternites light yellow. Halteres rather short, 

 pale, the knob brown. Legs, coxae and trochanters light yellow; femora 

 pale whitish broadly tipped with dark brown; tibiae with the extreme base 

 and tip narrowly dark brown; tarsi white, the apical segments becoming a 

 light brown. Wings light gray, the veins brown. Venation : see pi. iv, fig. 4. 



Abdomen dai'k brownish black throughout. 



Female. — Similar, the abdomen of a lighter brown, especially the stern- 

 ites which are ringed with darker apically. 



Habitat. — Bartica, December 10, 1912 to February 8, 1913. 



Holotype, cf, Bartica, January 28,1913. 



Allotype, 9 , topotypic, December 10, 1912. 



Paratypes, 9, topotypic, February 8, 1913; another specimen 

 with the abdomen broken, topotypic, January 21, 1913, in deep 

 swamps. 



This species is the largest and most showy of the forms known to 

 me. It may be easily recognized by the black tibial bases. 



Tribe Eriopterini 

 Genus CONOMYIA Meigen 

 1818. Gonomyia Meigen, Syst. Beschr., i, 146. 



Subgenus LEIPONEURA Skuse 



1^89. Leiponeura Skuse, Proc. Linn. Soc. N. S. Wales, ser. 2, iv, 795. 



This group was represented in the collection by a great number 



of specimens the majority of which were females. It is no longer 



possible to determine isolated females in this genus or in Molophilus 



