472 INSECTS INJURIOUS TO VEGETATION. 



crop is thereby rendered worthless. The maggots, when fully 

 grown, are nearly one eighth of an inch long. Mr. JVIarsham 

 and Mr. Kirby found some of them changed to pupae, within 

 the ears of the wheat, and from these they obtained the fly 

 early in September. The pupa, represented by them, is rather 

 smaller than the full-grown maggot, of a brownish yellow 

 color, and of an oblong oval form, tapering at each end. The 

 pupae found in the ears were very few in number, scarcely one 

 to fifty of the maggots. Hence Mr. Kirby supposes, that the 

 latter are not ordinarily transformed to flies before the spring. 

 Towards the end of September he carefully took pfl" the skin 

 of one of them, and found that the insect within still retained 

 the maggot form, and conjectures that the pupa is not usually 

 complete until the following spring. It is evident, from these 

 observations, that the English naturalists, above named, re- 

 garded the insect as having entered upon the pupa state when 

 it ceased feeding and became quiescent, at which time Mr. 

 Kirby found it generally to adhere somewhat to the grain. In 

 applying to it, in this condition, the name of chrysalis or pupa, 

 and describing it as such, before it exhibited any trace of " the 

 lineaments of the future fly," and while " still in the form of 

 the larva," they followed the common usage of naturalists, as 

 stated in my account of the Hessian fly. They cannot, there- 

 fore, be said to have mistaken the larva for the matured pupa; 

 the remarks of Mr. Kirby prove that he was well aware of the 

 difference between them. Mr. Kirby, however, was mistaken 

 in his conjecture that "the insect inclosed itself in a thin 

 membrane to protect itself from the cold of the winter;" the 

 membrane, referred to, being merely the outer skin of the larva, 

 loosened previously to being cast off entirely ; a process which 

 he did not observe. According to Mr. Gorrie, the maggots 

 quit the ears of the wheat by the first of August, descend to 

 the ground, and go into it to the depth of half an inch. That 

 they remain here unchanged through the winter, and finish 

 their transformations, and come out of the ground in the 

 winged form, in the spring, when the wheat is about to blos- 

 som, is rendered probable from the great number of the flies 

 found by Mr. Shirreff, in the month of June, in all the fields 



