1 52 Zoology of Colorado 



be the closely related but very common Melanoplus atlanis, a per- 

 manent resident of Colorado. Nevertheless, Mr. Morgan Hebard 

 of Philadelphia records finding specimens of M. spretus in the 

 Garden of the Gods and at Mountain View, Pike's Peak, in 

 August, 1904; but whether they had bred in the locality he was 

 unable to determine. In M. atlanis the tegmina or upper wings 

 are about 20 mm. long in both sexes; but in M. spretus, as befits 

 a migratory species, they are considerably longer, about 26.5 

 mm. in the male, and 27.5 in the female. Both species have the 

 hind tibia red, except that in atlanis variations occur in which 

 they are blue (variety caeruleipes) or pale yellow. These varia- 

 tions are interesting, because they show that flie Acridiinae have 

 pigments in their legs similar to those found so conspicuously 

 in the CEdipodinae. 



The resident M. atlanis*, and other species of the same 

 genus, do a great deal of damage to crops every year, but do not 

 cause sudden and dramatic castatrophe in the manner of M. 

 spretus. The numbers of these insects vary in different seasons, 

 and recently the entomologists of the U. S. Bureau of Entomology 

 have been making intensive studies of the early stages, in order 

 to recognize the unusual abundance of any injurious species 

 while it is young, and can be controlled by poisons before any 

 serious damage has been done. This involves minute and dis- 

 criminating studies, for several of the kinds are very much alike. 



A much larger Melanoplus, about 27 (male) to 37 (female) 

 mm. long, very common in Colorado, is M. bivittatus, described 

 by Say in 1825. It is easily recognized by the pair of yellowish 

 stripes running along each side of the thorax above, extending 

 forward on to the head above the eyes, and backward on to the 

 tegmina, where they converge when the wings are closed. A 

 further distinguishing mark is the broad, continuous black stripe 

 along the outer side of the thickened hind femora. On account 

 of its large size and abundance, this yellow-striped locust is likely 

 to be particularly troublesome, and Professor Gillette expressed 

 the opinion that it was the most injurious species in Colorado. 

 It will attack alfalfa, clover, grass, corn, vegetables, and in fact 



*Hebard has proposed to reduce M. atlanis Riley to subspecific rank under M. mexicanus. 

 It has also been maintained of late that M. atlanis and M. spretus are forms of a single species. 

 The name mexicanus is the oldest (1861), then spretus (1866), then atlanis (1875). Hence we 

 should have to write M. mexicanus spretus for the Rocky Mountain locust. 



