197 



Hessian Fly which ought to be explained or removed. The 

 first and most important is in the number of the joints of the 

 antennse. These ought to be the same in all specimens of the 

 Hessian Fly, or in all specimens of the same sex ; for I can 

 conceive and admit that the male may have one joint or two 

 joints more than the female. 



In Elsworth's Report on Patents, 1845, p. 162, you state 

 that " the antennas consist each of from fourteen to seventeen 

 oval joints, besides the basal joint, which appears double"; that 

 is, the antennas are sixteen- to nineteen-jointed. 



In your letter to me, dated June 7, 1841, you stated that the 

 antennse- of females as well of males were " seventeen to 

 nineteen articulate," — '•'• articulus primus turbmatus, secmidus 

 globosus" etc., noticing the difference in the form of the 

 following joints in the two sexes. 



Dr. A. Fitch, in his account of the Hessian Fly, p. 41, states 

 that the antennge are "composed of sixteen joints"; "the two" 

 basal joints are globular, and compact or not separated by an 

 intervening filament, and exceed the following joints in diam- 

 eter." This is given in his description of the female. He 

 does not say that the number differs in the male. His figure 

 of the ^ shows sixteen joints ; that of the 9 fifteen joints. 

 If in this case the basal is to be counted as two joints, the male, 

 according to Dr. Fitch's figures, will have seventeen and the 

 female sixteen joints to the antennse. 



Say does not give the number of joints in either sex (see 

 Journ. Acad. Nat. Sc, I, pp. 45, 46). In Lesueur's rather 

 coarse drawing (ibid, opposite page 64), the enlarged figures 

 of the antenntB (3, a and b) give fifteen joints in each sex ; 

 probably the double basal joint was omitted. The figures 2 

 a and b also show only fifteen joints in each sex. 



Have you observed a greater number of joints in the anten- 

 nse of the males than in those of the females? Do you know 

 whether Dr. Fitch has noticed the like difference ? or is the 

 difference in his figure accidental? In insects so small and 



