OF THE FAEM AIs^D GAEDEI^". 



127 



external surface of the stem; whereas, the true Joint- 

 worm always inhabits a smooth egg-shaped cell in the in- 

 ternal substance of that stem. 



XATUEAL HISTOKY OF THE JOIis"T-WOEM. 



The mode in which the Joint-worm produces its de- 

 structive effects upon small grain, may be readily ex- 

 plained. Xot only is the sap extracted on its course to 

 the ear, in order to form the abnormal woody enlargement 

 or gall, in which the larvae are imbedded, each in his 

 own private and peculiar cell, but a very large supply of 

 sap must be wasted in feeding the larvas themeslves. 

 Hence the ear that would otherwise be fully developed 

 becomes more or less shriveled; although we are told 

 that, in the case of barley more particularly, the plant 

 tillers out laterally, so as partially to supply the loss of 

 the main crop of ears. A similar phenomenon occurs 

 with almost all galls that grow upon a slender stem or 

 twig, that is, the stem or twig is more or less killed or 

 blasted thereby; but when a twig is quite large, this re- 

 sult often fails to be developed. 



The Joint-worm Fly (fig. 86, makes its api3ear- 

 ance in the Korth in the forepart and middle of June, 

 and in southern latitudes in the middle of ^lay. After 

 coupling in the usual manner, the female Joint-worm Fly 

 proceeds to lay her eggs in the stems of the growing grain. 

 The following excellent account of this operation, from 

 the pen of Mr. Pettit, is from the Canada Farmer": 



^ 'About the eighth of June, the perfect insects begin 

 to make their way out of the galls. ****** 

 I watched the growing barley, and on the tenth found 

 them actively at work ovipositing in the then healthy 

 stalks of the plant. Before commencing operations 

 they walk leisurely up one side of the plant as far as 

 the last leaf, and then down the other, apparently to 



