38 



rsrcHE. 



[March iSq?. 



DIPTERA FROM THE HEADWATERS OF THE GH.A RIVER.— I. 



BY C. II. TVI.ER TOWN-SEND, LAS CRUCES. N. MEX. 



The Rio Gila tallies its head in the 

 mountains of southwestern New Mexi- 

 co, in northern Grant and southern So- 

 corro counties. A short distance above 

 the Gila Hot Springs, which are about 

 forty miles by trail north of Silver City, 

 the river splits into its three forks, known 

 as the West Fork [sometimes called 

 Diamond Creek], the Middle Fork, 

 and the East Fork. These streams fol- 

 low down small caiions, which wind 

 up into the mountains. About fifteen 

 to eigiiteen miles up the first there oc- 

 cur what are known as the Falls of the 

 West Fork. Most of the West Fork 

 collecting in diptera, as well as other 

 insects, was done about two miles be- 

 low the falls, where the permanent 

 camp was made. It was all done in 

 the bottom of the caiion, the elevation 

 being probably about 7000 ft. Some 

 collecting was also done on the East 

 Fork, which was followed up past the 

 D-D-Bar ranch, and out into the basin 

 where, at the base of the Black Range, 

 is situated the V-Cross-T ranch. The 

 determinations of the East Fork diptera, 

 as well as of further material from the 

 West Fork, will appear in a second pa- 

 per. All the specimens were collected 

 by the writer, in July, 1S94. 



Chrysops ceras n. sp. West Fork. 

 Six 9 s. Four of them taken July 10, 

 about five miles above Gila Hot Springs ; 

 and the others July 16 and 17, about fif- 

 feen miles above, at camping place. 



Length, SJ to gi mm. \'ery near to 

 C. inegaceras Bell., ami C. taityceras 

 O. S. From C. viegaceras it difi'ers in 

 the presence of a cinereous border to 

 mesoscutum and scutellum ; all the tarsi 

 excluding metatarsi, blackish; the rest 

 of legs yellowish ; antemial joints i and 

 2 yellowish-brownish, no yellowish ves- 

 titure on face ; and in the yellowish-cin- 

 ereous borders to abdominal segments. 

 It agrees with C. megaceras in the 

 shape and length of the antennal joints 

 very closely, thus diflering markedly 

 from C. laiiyceras, from which it fur- 

 ther differs by the front and face being 

 cinereous pollinose, shape of frontal 

 callosity unlike an ace of spades, palpi 

 mostly blackish but partly yellowish, a 

 median linear vitta between the thoracic 

 pair, and in other minor points. Both 

 basal cells are wholly clear. The relative 

 length of the antennal joints in C. ceras 

 is about 3J (rarely 4) : t, : \h [some- 

 times 1 51- The first and second joint 

 seem sometimes to be almost equal, and 

 the third is often only half as long as 

 the second. It will thus be seen that 

 this species goes a step farther in this 

 particular direction of antennal devel- 

 opment than does Z. megaceras. which 

 is the nearest species to it in this regard, 

 next to megaceras being tanyceras. It 

 may be noted also in this connection 

 that these three species are all of a 

 general brownish color, and have the 

 wings obscurely clouded. 



