780 BULLETIN UNITED STATES GEOLOGICAL SIIEVEY. 



Fam. TABANID^. 



Pangonia incisa Wied. — Pangonia incisuraUs Say. 



Occurred at Colorado Spriugs, flying over the beads of simflower, but 

 not common, August 17. 



Clirysops fulvaster O. S. 



Common in the western suburbs of Denver, among the willow trees, 

 August 5; one specimen was captured in the pine woods on the side of 

 the mountain adjoining Clear Creek Caiion, August 7. They have the 

 same vicious i)ropensities common to our species of the Atlantic region, 

 in flying upon the unprotected face or hands of human beings, and 

 quickly inflicting a wound, which smarts keenly. 



Fam. BOMBYLIDiE. 



PJxoprosojja decora Loew. 

 Occurs on the plains near Denver City, August 5 and later. 



Exoprosopa dorcadion O. S. 



This beautiful species was moderately common on the low hills west 

 of Denver, August 8 to 18. One specimen was also found at CaQou City. 



Many of the specimens of this and other Piptera were more or less 

 denuded of their fur by the driving winds, loaded with fine sand, which 

 preceded the rain-storms. Sometimes after the showers, these and other 

 hairy insects were found lying on the ground near plants soaked with 

 wet, and with scarcely a hair or scale of the upper surface remaining. 

 At Canon City, the winds, loaded with fine sand, were more intolerable 

 than at any other place that I visited; and at that iioint I saw many 

 insects destroyed and denuded by their agency. No doubt, these sand 

 blasts lend their influence in determining the various shapes of many of 

 the sandstone pillars with which the plains and highlands of Colorado 

 are studded near the mountains and in the parks. 



Exoprosopa tituhans O. S. 



In the suburbs of the city of Denver, lodging upon bare sandy spots 

 m the midst of the patches of flowers and weeds, August 5 to 8. 



JExoprosopa dodians O. S. 



Two specimens, one from Manitou and the other from the hill- side 

 near Colorado Springs, August 13 to 16. 



These very attractive insects were seen at almost every locality on 

 the plains and foot-hills, and also in Clear Creek CaSon. They balance 

 over the bare sandy spots in the bright sunshine, and then dash sud- 

 denly and settle upon the ground with their wings fully expanded. 

 Doubtless many other species and varieties might have been captured 

 if my time could have been so employed. 



Pipalta serpentina O. S. 



I met with it only in Clear Creek, where but a few specimens were 

 seen flying near the road and lodging upon the rocks, August 6 and 7^ 



