408 RAVAGES OF IXSECTS. 



witli hairs.* The female is furnished with a retractile ovi- 

 positor, four times as long as the bod}^ and as fine as a 

 hair, for depositing her eggs, which she does in the glnmes 

 of the florets of the grain. The following account of its 

 proceedings is given by Mr. Shireff, an intelligent farmer 

 of East Lothian : — 



"Wheat-flies," he says, " vrere first observed here this 

 season on the evening of the 21st of June; and, from the 

 vast number seen, it is probable a few of them may have 

 been in existence some days previous. The eggs were 

 visible on the 23rd, the larv86 on the 30th of that month, 

 and the pupa3 on the 29th of Jul}^ The flies were observed 

 depositing eggs on the 28th, and finally disappeared on 

 the 30th of July ; thus having existed throughout a period of 

 thirty -nine da^^s. 



" The flies were observed to frequent the wheat-plant, 

 including the thick-rooted couch-grass (Triticum repens). 

 They generally reposed on the lower parts of the stems 

 during the dary, and became active about sunset, except 

 when the wind was high. I have, however, seen them 

 flying about on cloudy mornings, till seven o'clock ; and, 

 upon one occasion, witnessed them depositing. their eggs, 

 in a shaded situation, at two in the afternoon. Their move- 

 ments appear to be influenced by the rays of light, of which 

 they seem impatient, being active w^hen the sun is below or 

 near 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 

 their eggs on ; and as one side only of the ear is exposed 

 when the plant is in this stage of growtli, the other side 

 generally remained miinjured 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 adhering 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 



* Linn. Trans., vol. iii. p. 2-13; iv. 234-240; v. 96. 



