Insects 179 



are noteworthy as carriers of the germs of disease, some annoy us 

 by their bites, some attack our crops and others our domestic 

 animals, but others confer a benefit by devouring injurious insects. 

 Although there are only two fuctional wings, the hind pair exists 

 in rudimentary form, being modified into small stalks with a knob 

 at the end, called hal teres. 



Diptera are very interesting from the standpoint of evolution. 

 A group of great antiquity, they have reached in certain forms, 

 such as the house fly, a very high degree of specialization. At 

 the same time, many of the more primitive types, such as the 

 crane-flies, have survived in great numbers, and we have a series 

 showing various degrees of modification. In the present account 

 it is possible to discuss only some of the more interesting families. 



Tipulidae or Crane-flies 



These long-legged insects, called daddy-long-legs in England, 

 are extremely abundant, some of large size, others quite minute. 

 Dr. C. P. Alexander, in his work on the Crane-flies of New York, 

 published (1919, 1920) by Cornell University, has given an ad- 

 mirable account of the family, describing both structure and 

 habits. I have catalogued over 50 species from Colorado, but 

 many more exist. The fossil forms are also very numerous, and 

 at Florissant we find species of Tipula in the Miocene shales, 

 still showing the markings of the wings and abdomen. The 

 larvae of some species of Tipula are very destructive to grass 

 and cereals. 



The Dixidae, an interesting family of small flies, was added 

 to our list when Mr. Scott Gale found the new species Dixa univer- 

 sitatis Cockerell on the University of Colorado campus, September 

 27. 1926. 



Chironomidae 



A family of small gnats, often taken for mosquitoes. The 

 typical Chironomidae, often found on windows, are quite inof- 

 fensive. Some of them have red worm-like larvae, called blood- 

 worms, living in stagnant water. The group Ceratopogoninae, 

 sometimes regarded as a separate family, includes the excessively 

 minute punkies, which will come through an ordinary mosquito- 

 screen, and bite viciously. Troublesome species in Colorado are 



