UHLER ON INSECTS. 363 



spondee! with similar ones on the sliores of the ocean and bays of Mary- 

 land, where the S.fasciaUis abounds. 



The pretty Odontomyia nigrirostris Loew occurred singly upon the sun- 

 flowers at Colorado City. It sometimes remained over night upon the 

 flowers, but was often seen flying toward them in the bright sunlight. 

 Other species were taken in the same locality, most of which were not 

 nearly so numerous as the first mentioned. 



Mosquitos were very numerous on plants in marshy situations and 

 near them, particularly in the western suburbs of Denver. 



Muscidce were tolerably common in houses: but several forms of Sar- 

 cophaga, Desia, etc., were distributed all over the more fertile parts of the 

 plains and canons. 



TlpuUdcc were scarce in every locality that I visited. Several very 

 neat forms of Tri/peta were common on the i)lains in the vicinity of water. 



Of all the orders of the insects, none were more abundantly and con- 

 spicuously represented than the Hymenoptera ; although of one or two 

 families, such as the Saw-flies and UroceridcE, not a single example was 

 seen. Cynipidw were very scarce, and represented only by a few small 

 galls upon stunted oaks near Manitou. Ants were numerous; the 

 ground in loose soils at the mouth of the CaQon of the Arkansas was 

 everywhere undermined by a species with a red head. A species closely 

 resembling Formica riifa makes hills of sand on most parts of the plains 

 within a few miles from the mountains. They construct hillocks rang- 

 ing in height from 9 inches to 1| feet, and from 2 to 3 feet in width at 

 base. These nests are dome-shaped, constructed of the soil brought 

 from beneath the surface, and covered on the outer surface with water- 

 l^roof clay-earth, cementing variously colored pebbles all over the sur- 

 face. Their appearance is sometimes that of a loosely made mosaic, 

 and is very conspicuous in some places, owing to the different colors of 

 the pebbles and bits of minerals used in construction. In general, the 

 entrance-holes are situated on the side away from the mountains, usually 

 on the southeast side, opposite the direction of the prevailing rain- 

 storms. Some of them were placed quite near the prairie-dog mounds ; 

 but in no instance did I observe any of them to be connected with 

 them. Occasionally a gopher-burrow may be seen to penetrate one of 

 the ant-hills, and in all such cases I could not detect the presence of the 

 ants. They were in no wise difiFerent from the others, which were 

 abundantly peopled by the ants. But as other hills were found desti- 

 tute of ants, I presumed that these had also been deserted before being 

 occupied by the gophers. 



In this connection, although they do not belong to this order, it may 

 be not amiss to speak of the white ants. They were found abundantly 

 beneath loose bark in the region near Canon City, but more particularly 

 under stones on the hill-sides adjacent to Colorado Springs. All the 

 sexes and forms were present in the unwinged stages. Xymphs of 

 males and females had rudiments of the wing-cases, but none had 



12 HB 



