DIMOEPHISM IN CHAITOPHORUS ACERIS. 131 



that I do not doubt that it emerged from it. It is of 

 consequence to remark that the new insect is of a higher 

 type, for its antennas are more completely jointed, and 

 its nectaries are fully formed.* 



These observations do not wholly agree with those 

 made by Balbiani and Signoret in then' memoir on 

 Periphyllus. They describe three kinds of embryo 

 " enceinte," one with folioles, another pubescent, and a 

 third having a mixed character, that is to say, having 

 hairs partly developed into folioles. These are when 

 first born enveloped in a delicate membrane, from 

 which the insects shortly afterwards free themselves. 

 Again, they remark " that it was only the scattered 

 {dessemerees) winged and apterous females which 

 gave us the foliated embryo, but that the associated 

 females (agglomerees) furnished forms hirsute like the 

 mother." 



Again, they say, the normal foetus has much the 

 same form as the foliated foetus, but the lamella are 

 represented by bristles, and the abdomen is not covered 

 with " marquetrie." Besides this, the insect undergoes 

 sundry moults and eventually becomes winged. 



I have above described the black alate female of this 

 Aphis, which answers to Koch's figure. This insect 

 cannot be the same as that which Lichtenstein found, 

 and says he is satisfied was a male, and which also he 

 refers to Koch's figure 19. The black insect I 

 I have figured, Plate LXXVIII, fig. 3, is undoubtedly 

 a female, and, contrary to Balbiani and Signoret's 

 experience, it yielded by dissection, June 25th, nine 

 young, each enclosed in its own membrane. By mani- 

 pulations with needles these unmistakably showed, by 

 the presence of dorsal plating and the characteristic 

 folioles, that they were all of the abnormal kind. 

 Several of the pseudomorphic young were moreover 

 scattered on the same leaf which supported this Aphis, 

 and I conclude were born of her. 



* This observation would suggest a doubt wlietber the uou- develop, 

 mental rule, as regards this dimorpb, is strictly rigid. 



