378 THE CANADIAN ENTOMOLOGIST 



The development of these organs affords a good systematic char- 

 acter and is correlated in certain instances at least ,with important 

 modifications in habit. 



Wings : — The organs of flight are of great value in taxonomic 

 work and, in this family, present satisfactory characters for the 

 delimitation of subfamilies and tribes. There is a cross-vein con- 

 necting subcosta and the third vein which occurs in a well-developed 

 condition in the Lestremiinse and the Epidosariae, it being rudimen- 

 tary or absent in the other groups except certain Heteropezinae. 

 The presence of the fourth vein is limited to the Lestremiinae, in 

 which subfamily it may be either forked or simple. The fifth vein 

 also presents important modifications in that it may be simple, in 

 which case there is frequently a sixth vein, or forked, in which latter 

 instance the sixth has become partly fused with the fifth. Certain 

 genera in the Heteropezinae are remarkable because of the weak 

 wings and greatly reduced venation. 



Tarsi: — -The normal number in segments is five, members of 

 the Itonididinae invariably having the first segment greatly re- 

 duced. Certain genera of the Heteropezinae have four; others 

 three, and in Oligarces there are but two tarsal segments. The 

 claws may be simple, pectinate or dentate. They vary greatly in 

 development and the same is true of the pulvilH. 



There are other structures presenting equally significant modi- 

 fications. This is particularly true of the generative organs and is 

 especially well shown in the modified ovipositor which reaches an 

 extreme development in the needle-shaped organ of Asphondylia, 

 an instrument evidently designed for the piercing of thick bud 

 tissues so that the egg may be deposited close to the growing point 

 and in a place where conditions are most favourable for the de- 

 velopment of the young. 



It wiM be seen from the foregoing that the gall midges 

 can not be counted as particularly strong or prolific forms, yet they 

 have been able to maintain themselves largely by what we term 

 evasive adaptations, which have resulted in their securing a very 

 large degree of protection at the expense of the host plant. This 

 summary is not intended to exhaust the subject, but is presented 

 for the purpose of calling attention to a group exhibiting 

 numerous unsolved and exceedingly interesting biological and 

 morphological problems. There is perhaps no insect family better 



