582 DIPTEBA. 



seed through the middle of the stem, and, having reached a 

 proper height, escapes from the hollow of the straw to the 

 outside, where it takes the pupa or flax-seed state. The 

 fact that the Hessian fly does ordinarily lay her eggs on the 

 young leaves of wheat, barley, and rye, both in the spring 

 and in the autumn, is too well authenticated to admit of any 

 doubt. If, therefore, the observations of Miss Morris are 

 found to be equally correct, they will serve to show, still 

 more than the foregoing history, how variable and extraordi- 

 nary is the economy of this insect, and how great are the 

 resources wherewith it is provided for the continuation of its 

 kind. 



The foregoing remarks were written in 1841. Since that 

 time, the communication, to which they refer, has been 

 printed,* and this has been followed by the publication of 

 several other articles,* on the same subject, by Miss Morris. 

 This ingenious and persevering lady has also favored me 

 with letters concerning her investigations, and with some 

 of the flies. The latter were sent, as she says, " to convince 

 me, at least, that she had not mistaken a curculio, moth, 

 or bee for a Cecidomyia." Miss Morris has come to the 

 conclusion that this insect is a different species from the 

 Hessian fly, for which it had previously been mistaken, 

 and has given to it the name of Cecidomyia culmicola. Ac- 

 cording to her, the fly " deposits its eggs early in June on 

 the grain, in or over the germ. The eggs remain unhatched 

 until the grain germinates, but when the plant has grown 

 about three or four inches, the worm may be seen, with 

 the aid of a strong magnifying-glass, feeding above the top 

 joint, in the centre of the culm, where it remains until it 

 arrives at maturity. Should this occur before the culm 

 has become hard, the worm eats its way through the joint, 

 inside of the straw, and makes its escape at the root, as- 



* Transactions of the American Philosophical Society, Philadelphia, New 

 Series, Vol. VIII. p. 48. Proceedings of the Academy of Natural Sciences, 

 Philadelphia, Vol. I. p. 66; Vol. III. p. 238; and Vol. IV. p. 194. 



