Some Account of the Wheat Fly, 44.9 



few days after their appearance. They generally reposed on 

 the lower part of the culms during the day, and became active 

 about sunset, except when the wind was high. I have, how- 

 ever, seen them flying about in cloudy mornings, till seven 

 o'clock; and, upon one occasion, witnessed them depositing 

 their eggs, in a shaded situation, at two in the afternoon. I 

 could not determine when the flies retired to rest for the night, 

 as they continued active while light enabled me to distinguish 

 objects, and I doubt if they are in the habit of doing so. Their 

 movements appear to be influenced by the rays of the sun, of 

 which they seem impatient,* being active when the sun is below 

 or near to the horizon ; they frequent the most umbrageous 

 part of the crop, and shun that which is deficient in foliage. 



The flies almost invariably preferred the ears emerging 

 from the vagina to those farther advanced, for depositing eggs 

 on ; and as one side only of the ear is exposed when the plant 

 is in this stage of growth, the other side generally remained 

 uninjured. The fly deserted the fields as the crop advanced 

 towards maturity, and were found longest on the spring-sown 

 portion of the crop. It seemed to feed on the gum ad- 

 hering to the newly emerged ears ; and as there is a great 

 diversity in the time of sowing wheat in this neighbourhood, 

 and consequently of the ears escaping from the vagina, I attri- 

 bute the unusual length of time it has existed this season, to 

 the supply of food thus gradually furnished. 



The fly deposits its eggs with much intensity, and may easily 

 be taken when so employed. Upon one occasion, I numbered 

 thirty-five flies on a single ear ; and, after carrying it a distance 

 of a quarter of a mile, six of them still continued to deposit 

 eggs. At another time, I shook a fly, then laying, between the 

 face and glass of my watch, where it deposited several eggs, 

 although invariably interrupted by the revolution of the mo- 

 ment hand. 



The ovidepositor of the fly is of considerable length, perhaps 

 four times that of the body, and so minute, that it appears 

 doubtful whether the eggs pass along the interior or exterior 

 surface. The depositor can be extended and withdrawn at 

 pleasure, and is seldom visible unless the fly is depositing eggs. 

 The figure of the fly given by Mr. Kirby (Vol.1, fig. 91.), and 

 which has been copied into different periodicals and news- 

 papers, represents it flying, with the depositor extended, and 

 is so unlike the fly when seen, that agriculturists are unable to 

 recognise the fly from the figure. 



The hue of the fly is orange ; the wings transparent, and of 

 changing colour according to the light in which they are viewed. 

 On several occasions I observed a fly, differing from others in 



