154 Zoology of Colorado 



edged with blackish, and the hind femora have a red garter-like 

 band near the end. In H. speciosus of Scudder the thorax above 

 appears to be slightly keeled, the keel having a rosy tint. The 

 tegmina are short but still functional; in H. viridis they are very 

 well developed. H. speciosus was found in numbers at White 

 Rocks, Boulder County, feeding upon the horse-weed, Cycla- 

 chaena xanthiifolia* On the wild sage brush (Artemisia) at low 

 altitudes one may find the curious little Hypochlora alba of Dodge, 

 pale like the sage, a sort of whitish green, and quite unable to fly. 

 It is interesting to note that certain Orthoptera are confined to 

 one genus of plants, while others are polyphagous, feeding on 

 many. 



ODONATA 



The Odonata, or dragon-flies, are recognisable by the more 

 or less slender body, and four membranous, finely netted, wings. 

 Sometimes they may be confused with the Ant-lion-flies, but 

 the details of the wing venation are different, and a glance at the 

 antennae will be decisive. The antennae of the dragon-flies are 

 so short that they seem to be absent on hasty examination, while 

 those of the ant-lion-flies are always conspicuous. The immature 

 stages of dragon-flies are passed in the water, and exhibit some 

 very remarkable characters. The labium or lower lip is greatly 

 enlarged, forming a peculiar structure called the mask, which fits 

 over the face, and can be extended to grasp the prey of this 

 predatory insect. The details of the structure of this mask differ 

 in the various groups of dragon-flies, and are used as a means of 

 classification. The immature dragon-fly has been rather absurdly 

 called the nymph, for it has neither beauty or elegance. Corn- 

 stock has recently proposed to use the term naiad, but this is 

 inadmissable, because it has long ago been applied to the fresh- 

 water mussels. Thus Lea in 1829 published a "Description of 

 a New Genus of Naiades," and Simpson, in 1900, published a 

 "Synopsis of the Naiades, or Pearly Freshwater Mussels." Till- 

 yard, with some reason, argues that the simple and obvious thing 

 to do is to speak simply of the larva, whether old or young, as 

 there is no distinctly differentiated pupa stage in these insects. 



*Rydberg writes this C. xarxthifolia; but the name means with leaves like those of a 

 cocklebur {Xanthium), and so should be xanthiifolia. 



