ART. 20 NOTES ON THE MUSCOID FLIES EEINHAKD 5 



domen in the female and yellow legs in both sexes. The host rela- 

 tionships of flavescens are unknown. 



Genus OPSODEXIA Townsend 



Townsend established the genus by the mere designation of a type 

 species ^ without giving any description of the generic characters. 

 The type of Opsodexia is Chaetona hicolor Coquillett. I am in- 

 debted to Dr. J. M. Aldrich for pointing out these facts to me in 

 correspondence and placing two apparently undescribed species at 

 my disposal. 



Generic cJiaracters, from the type species. — Postscutellum only 

 slightly developed and membranous above. Occiput somewhat 

 swollen below; cheeks one-fourth the eye height. Front in male 

 greatly narrowed above; frontals in two rows, stopping at base of 

 antennae, the uppermost hairlike situated considerably before ante- 

 rior ocellus. Antennae inserted slightly below middle of eye, slightly 

 shorter than face, third joint three times the length of second ; arista 

 with long hair above and beneath. Face not keeled ; ridges flattened 

 below, with a few short bristles above vibrissae, which are well de- 

 veloped and situated on level with oral margin; parafacials narrow, 

 with short hairs above. Proboscis short, fleshy ; palpi normal. Eyes 

 bare. 



Thoracic chaetotaxy : Dorsocentral 2, 3 ; acrostichal 0, 1 (in trans- 

 verse line with hindmost pair of dorsocentrals) ; humeral 2; post- 

 humeral 1 ; presutural 1 ; notopleural 2 ; pteropleural ; supraalar 3 

 (posterior one bairlike) ; intraalar 2 (none near suture) ; postalar 2; 

 sternopleural 2; scutellum with one marginal pair near base, a 

 strongly developed decussate apical pair, and a pair of rather weak 

 preapical and discal ; 'disk with numerous erect fine hairs. 



Abdomen without discal macrochaetae except on fourth segment; 

 segments 2 to 4 with marginal rows ; first without median marginals. 

 Wings normal; fourth vein with an oblique bend ending at or just 

 before apex; hind cross vein oblique to fourth, which it joins slightly 

 nearer the bend than small cross vein ; last section of fifth vein very 

 short. 



The genus resembles Opelousia in having a short fleshy proboscis ; 

 flat unkeeled face; front of male greatly narrowed above without 

 any frontal bristles immediately before triangle, the uppermost 

 being very small; a conspicuous patch of infrasquamal hairs; no 

 presutural acrostichals, etc. It differs principally in the slight de- 

 velopment of the postscutellum, arista with longer and denser hairs ; 

 hind cross vein less erect; parafacials with short hairs above. 



2 Proc. Biol. Soc. Wash., vol. 28, p. 20, 1915. 



