The Scottish JVatura/ist. 31 



galls out of which it develops could be made by such an ovi- 

 positor. Similar observations gave the result that ApJiilothrix 

 radicis is the alternating generation of Andriais uodiili, and 

 Aphilothrix Sieholdii of Audricus tcstaceipes. Neither Aphilothi'ix 

 nor Andriais develop in the same year ; each of those genera 

 needs two years for its development ; therefore the whole cycle 

 runs here through four years, and till now only half the cycle of 

 Ajid7'icus bred from Aphilothrix galls has been ascertained by 

 observation. 



" I think there can be no doubt that the agamous C. q. acicu- 

 lata is the winter form of the bisexual C. q. spongifica^ just as 

 Neu7-oterus and Dryophanta ; but here both species have the 

 same kind of gall, and both species are less different than those 

 above quoted. 



" The remarkable success of Dr Adler's experiments with the 

 Hymenopterous galls induced me to compare the rather large 

 collection of Dipterous galls from Europe and America belonging 

 to the Museum. I found directly some forms entirely similar 

 and corresponding to the alternating galls of Cynips ; but the 

 collection is rather poor in bred specimens of the insects. Just 

 in the presence of the judicious and sober observations of Dr 

 Adler, it would not be proper to say more than that it is not 

 difficult to point out galls of Cecidomyia similar to both forms 

 of the alternating Cyjiips galls. It is to be presumed that in 

 Cecidomyia, as well as in Cynips, the form of the ovipositor will 

 be different; but such investigations can scarcely be successful 

 with dry specimens. 



'■'- 1 may add one observation, made by myself, by which it is at 

 least probable that bisexual species of Cecidomyia may also pro- 

 pagate by parthenogenesis. Some twenty years ago, occupied 

 with the study. of insects obnoxious to agriculture in Prussia, I 

 had stalks w-ith cocoons of Cecidomyia destructor in corked glass 

 tubes. In one of them I raised a single female, and was sure 

 that no other cocoon was present. The female laid a number of 

 eggs on the glass, which, after a few days, began to develop so far 

 that the embryo and the segmentations of it were clearly visible. 

 By some mischance the glass tube was left in sunlight and the 

 development stopped. Though I have not been able since to 

 repeat the observation, I am sure that I was not mistaken. I 

 think it is justifiable to presume a possible parthenogenesis for 

 Cecidomyia, which, if proved, may lead to successful results con- 

 cerning the destruction of this dangerous pest. 



