50 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



partially accomplished, in that, under the proper climatic con- 

 ditions, males and eggs do not appear in certain species whilo 

 in colonies of the same species living under other conditions 

 they do occur. 



Granting the above premises, we believe that in these inter- 

 mediates we have to do solely with transitional forms between 

 more primitive conditions on one hand and more advanced con- 

 ditions on the other. We feel confident also, that all these inter- 

 mediates are of equal value. The very fact that variants have 

 been discovered in so many different species, having such diverse 

 habits, seems to us to preclude the possibility that these arise 

 from different fundamental causes. The only difference is that 

 the forms in A. pomi and similar species and the intermediate 

 sexuparse of various Phylloxera are varying in one characteristic, 

 the elimination of wings, while the virginoparous forms in Ph. 

 vastatrix and in the Chermesinse are varying in two characters; 

 the elimination of wings and the elimination of sexes. The inter- 

 mediates described by Hunter and by Webster and Phillips fall 

 into at least two classes, the elimination of wings and the elimi- 

 nation of ovipara. Some of the forms are intermediate in both 

 groups, some only in one. It is possible, also, that there is here, 

 a variation between sexual and parthenogenetic reproduction, 

 but as the offspring were not reared this point cannot be 

 determined. 



We feel confident that, in the final analysis, these forms are 

 not the result of promiscuous variations, but of deviations along 

 definite lines, which are uniform for the entire family; that 

 changes in outward form are always from alate to apterous; 

 and that variations in the mode of reproduction progress from 

 sexual to parthenogenetic and from oviparous to viviparous. 



If we are correct in this matter then we are dealing with a 

 group of insects which are at present in an unstable condition 

 and in the various intermediates we are observing the steps by 

 which the more advanced conditions are attained. 



BIBLIOGRAPHY. 



(1) BALBIANI, (1884) Le Phylloxera du chene et le Phylloxera de la 



vigne. Paris, 1884. (Gauthier-Villars imprimeur-libraire.) 



(2) BORNER, O., (1908) Erne Monographische Studie uber die Cher- 



miden. Arbeit, a. d. Kais. Biol. Anstalt. Bd. 6, Heft. 2, p. 45. 



(3) DREYFUS, L., (1889) Neue Beobachtungen bei den Gattungen 



Chermes L. und Phylloxera Boyer de Fonsc. Zool. Anz., No. 300. 



(4) FATIO, (1876) Le Phylloxera dans le canton de Geneve d' aotit 



1875 a juillet 1876. Rapport au de"partement de 1'inte'rieur du 

 canton de Geneve. 1876. 



