92 UNIVERSITY OF COLORADO STUDIES 



adults are often sluggish, and if disturbed fall to the ground, yet 

 there are some species which are alert and troublesome to net. 



The larvae are, within their limits, very diverse. Many of them 

 feed on leaves and are either gregarious or solitary ; some of them are 

 leaf-miners; a few leaf rollers; some live in galls made either on the 

 leaf or twigs; others are internal feeders, living in trees, shrubs or 

 grasses. They live on the most diverse plants from ferns to composites. 

 The fern-feeders are a rather highly specialized group, while some of 

 the more generalized ones feed on the higher plants, as Rubus. This 

 would seem to indicate that they are either of recent origin, coming 

 into existence after the plants had become well established — in which 

 case we would assume that their food habits were specialized — or we 

 may assume that they are polyphyletic, i.e., had many ancestors. 

 It would be out of place to go into a phylogenetic discussion in this 

 short paper, but it may be stated that, judged from characters other 

 than food habits, the group is probably polyphyletic, or if they had 

 one common ancestor, it was at such a remote period that the inter- 

 mediate forms have long been extinct. 



For the study of Chalastogastra it is desirable that a binocular 

 microscope should be used. The ordinary hand lens does fairly well 

 for the larger forms, but the smaller forms can be studied to a much 

 greater advantage with the above-mentioned instrument. The 

 student should endeavor to master the characters of the head given 

 by Marlatt, 1896, Rohwer, 1909, and certain others which the writer 

 will be glad to explain, until they have been published in collected 

 form. The characters of the head are of great specific importance. 

 Generic and group characters are found on the body, more especially 

 the thorax, and one should become familiar with the thorax (see 

 Snodgrass, 1910). The wings are subject to much variation but 

 with a knowledge (gained only through experience) they can be used. 

 They are well treated by MacGillivray, 1906. 



The larvae of the western species are almost unknown and a study 

 of them would form an interesting and profitable piece of work for 

 someone to undertake. They have many food-plants, but probably 

 more would be found on the willows and birches than elsewhere. 



