THE CANADIAN ENTOMOLOGIST. 89 



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 

 Cynips 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. 



I may add one observation made by myself, by which it is at least 

 probable that bisexual species of Cecidomyia may also propagate by par- 

 thenogenesis. Some twenty years ago, occupied with the study of insects 

 obnoxious to agriculture in Prussia, I had stalks with cocoons of Cecid- 

 omyia 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 develop- 

 ment stopped. Though I have not been able since to repeat the observa- 

 tion, 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 concerning the destruction of this dangerous pest. 



After having studied Dr. Adler's papers, I remembered directly some 

 similar facts given by Mr. Lichtenstein in Stettin. Entom. Zeit, 1877, on 

 the Hemipterous genus Phylloxera ; the alternation is here very remark- 

 able. The bisexual form originates from pupae, which are produced by 

 larger winged forms, which possess no external sexual organs and can 

 therefore not copulate. Mr. Lichtenstein calls this form of propagation 

 anthogenesis. A certain similarity with Cynips consists in the fact that 

 the different forms of Phylloxera emigrate in spring and return in the 

 fall. So the well known Ph. vastatrix emigrates from the leaves to the 

 root of the same plant, and needs therefore no special winged forms for 

 the purpose of emigration. But Ph. quercus changes to another tree, and 

 needs therefore two winged forms, which are different one from the other. 

 One parthenogenetic form brings the summer colonies from Ilex to Kobur, 

 and another anthogenetic fall form brings them back from Robur to Ilex. 

 The fact that some species possess two different winged forms will proba- 

 bly reduce the number of the described winged species. Till now it is 

 only known that Ph. Lichtensteini is the anthogenetic form of Ph. quercus, 

 and Ph. Signoreti probably the same form of Ph. florcntiua. Mr. Lich- 

 tenstein presumes that many Pemphigus and Adclges will possess similar 



