130 THE CANADIAN ENTOMOLOGIST. 



Dr. A. Dohrn has made inquiries in Rome about the Hessian fly, but 

 without success. 



The passage quoted out of A. Costa's lectures is of prominent interest. 

 It proves without any doubt that the insect is not C. tritici, which never 

 lays the eggs between the stem and the leaf, and which has never the 

 coloration of the imago as given in the description. Both facts agree 

 perfectly well with C. destructor. The determination of a species of 

 Cecidomyia of course can not be considered to be doubtless before speci- 

 mens have been compared, the more as the short description contains 

 some statements which if based on personal observation, are entirely new. 



One of them is decidedly startling. I point to the fact that some larvae 

 after having completed their development, give place to an agamous re- 

 production. [Compito che hanno, queste larve, il loro sviluppo, mentre 

 talune danno luogo alle riproduzioni agamiche altre,* nel posto stesso in 

 cui trovansi si transformano in pupe delle quali dopo pochi giorni schin- 

 dono gl'insetti perfetti che depongono novelle uova.] 



I have purposely put the Italian text in brackets after the translation, 

 as the end of the passage seems to state that the larvfe which have an 

 agamous reproduction do not when full grown transform themselves into 

 pupse. A similar reproduction, as is well known, has been observed in 

 several species of Cecidomyia by Nic. Wagner, Meinert, Leuckart and 

 others — the so-called paedogenesis. It has never been observed till now 

 for the Hessian fly, and the principal reason for doubt that Mr. A. Costa 

 has really meant paedogenesis, is the fact that he has not expressed him- 

 self in a more explicit manner, though he must have been aware of the 

 importance of his statement. I should remark that Mr. Bait. Wagner 

 speaks indeed of two different kinds of larv^ of the Hessian fly. The 

 fact that females of the Hessian fly lay eggs without copulation was long 

 ago published by myself. These eggs developed so far that the segment- 

 ation of the embryo was visible. The glass tube containing the eggs 

 having unfortunately been left in the sunlight, no further development 

 could be observed. 



Mr. A. Costa states that the larv?e sometimes make niches by shaving 

 the wall of the stem. This is contrary to all other observations, which 

 state that these niches are made simply by pressure. Asa Fitch is very 

 explicit about these facts, but when he states that the larvae do not enter 

 the central cavity of the stem, he is largely at variance with the direct 

 observations of Mr. B. Wagner and myself. I have indeed still before me 



