9G Psyclie [June 



very remarkable instance of a highly specialized group of sexually 

 reproducing animals in which fertilization of the female reproduc- 

 tive cells as a* prelude to development has been reduced to an 

 apparently unnecessary and unessential physiological process. 



General Features of Amphigoxy in Aphids. 



In the amphigonous generation both sexes are, of course, repre- 

 sented. The presence of the male is the only characteristic of the 

 amphigonous generation. 



The main external characteristics of an amphigonous female 

 are the general absence of wings (Baker, 1930), and the presence 

 of an ovipositor in certain species (Buckton, 1882, p. 119). Davis 

 (1908) also noted the presence of "sensoria" on the hind tibia? 

 as a secondary sexual character of the amphigonous female, "at least 

 in the subfamilies Pemphiginse, Schizoneuringe, Lachininae and 

 Aphidinae."^ Internally, the most conspicuous features are the 

 presence of a spermatheca and a pair of collaterial glands. The 

 acessory glands, as well as the vagina, of which they are an evagi- 

 nation, and also the oviducts, are easily recognizable on account 

 of their relatively thick walls. The large amphigonous eggs and 

 their nurse cells are also very characteristic and are in evidence 

 in the ovaries early in the embryonic stage of the mother. Cleavage 

 and the formation of the blastoderm do not begin until after the 

 eggs are fertilized and deposited. The amphigonous female is 

 oviparous. The eggs are covered with a vitelline membrane and 

 chorion. 



General Features of Parthenogenesis in Aphids. 



Among the aphids of temperate countries, aphidologists distin- 

 guish between (1) "stem mothers," which are the parthenogenetic 

 individuals hatching from the overwintering amphigonous eggs, 

 and (2) later parthenogenetic generations. The former are typi- 

 cally apterous; the latter, either apterous or alate. In the fall 



2 The typical genus of Schizoneurinae, which is Schizoneura Hartig, 1837, 

 is considered by Baker (1920) as a synonym of Eriosoma Leach, 1818. He 

 grouped the latter under the tribe Eriosomatini of the subfamily Eriosoma- 

 tinae. The subfamily Pemphiginse has been reduced by the same author to 

 tribe Pemphigini under the subfamily Eriosomatinge; and Lachninse, to 

 Lachnini under Aphidinse. 



