DIPTERA. 455 



of the joints differs according to the sex; tiiose of the male 

 being globular, and those of the female, except at base, oblong 

 oval. In both they are surrounded with whorls of short hairs. 

 The dilFerence in the antenna? of the sexes has been pretty 

 well represented by Mr. Lesueur, in the plate designed to 

 accompany Mr. Say's description of the insect. 



The following brief history of the habits, and transforma- 

 tions of the Hessian fly will be found to agree essentially with 

 the excellent observations on this insect, written in the year 

 1797, by Dr. Isaac Chapman, and published in the fifth volume 

 of the "Memoirs of the Philadelphia Society for Promoting 

 Agriculture," and with the more fall and equally valuable 

 history of the insect, by Jonathan N. Havens, Esq., contained 

 in the first volume of the " Transactions of the Society for 

 the Promotion of Agriculture, &c., in New York." Mr. Her- 

 rick has kindly permitted me to make free use of his valuable 

 account of this insect, contained in the forty-first volume of 

 " The American Journal of Science," and of other information 

 communicated by him to me in various letters. He has spent 

 some time in carefully observing the habits of the fly, during 

 many years in succession, after having fitted himself for the 

 task by the study of the natural history of insects in general. 

 His statements therefore may be relied upon, as in the main 

 correct. Moreover, they are corroborated by the observations 

 of many other persons, published in various works, which have 

 been consulted in the course of my investigations. 



Of this insect, two broods or generations are brought to 

 maturity in the course of a year, and the flies appear in the 

 spring and autumn, but rather earher in the Southern and 

 Middle States than in New England. The transformations 

 of some in each brood appear to be retarded beyond the usual 

 time, as is found to be the case with many other insects; so 

 that the life of these individuals, from the egg to the winged 

 state, extends to a year or more in length, whereby the contin- 

 uation of the species in after years is made more sure. It has 

 frequently been asserted that the flies lay their eggs on the 

 grain in the ear; but whether this be true or not, it is certain 

 that they do lay their eggs on the young plants, and long 



