574 DIPTEKA. 



of the leaf." His remarks in Professor Silliman's Journal 

 are to the same effect. Other authorities on this point 

 might be mentioned ; but the foregoing are suflBcient, in 

 my opinion, to establish the fact, that the Hessian fly lays 

 her eggs on the leaves of wheat soon after the plants are up. 

 •' The number on a single leaf," says Mr. Herrick, " is often 

 twenty or thirty, and sometimes much greater. In these 

 cases many of the larvae must perish. The egg is about a 

 fiftieth of an inch long, and four thousandths of an inch in 

 diameter, cylindrical, translucent, and of a pale red color. 

 Mr. Tilghman was correct in supposing that the eggs would 

 hatch in less than fifteen days, under favorable circum- 

 stances ; for, if the weather be warm, they commonly hatch 

 in four days after they are laid. 



The maggots (Fig. 258, natural size), when they first 

 come out of the shells, are of a pale red color. 

 '^' ■ Forthwith they crawl down the leaf, and work 

 their way between it and the main stalk, passing 

 downwards till they come to a joint, just above 

 which they remain, a little below the surface of 

 the ground, with the head towards tlie root of 

 the plant. Having thus fixed themselves upon 

 the stalk, they become stationary, and never 

 move fi-om the place till their transformations 

 are completed. They do not eat the stalk, 

 neither do they penetrate within it, as some persons have 

 supposed, but they lie lengthwise upon its surface, cov- 

 ered by the lower part of the leaves, and are nourished 

 wholly by the sap, which they appear to take by suction. 

 They soon lose their reddish color, tm'n pale, and will 

 be found to be clouded with wliitish spots ; and through 

 their transparent skins a greenish stripe may be seen in 

 the middle of their bodies. As they increase in size, and 

 grow plump and firm, they become imbedded in the side 

 of the stem, by the pressure of their bodies upon the 

 growing plant. One maggot thus placed seldom destroys 



