126 BRITISH APHIDES. 



of the Hymenopteimm were laid, or tlie larvse from 

 them burrowed into their substance. Other examples 

 are on record in which certain parasites succeed in 

 ovipositing ivithin the eggs of their victims, but in such 

 cases probably the metamorphosis of the parasite is 

 deferred until the larval stage of the infected insect is 

 reached. Probably the parasites above noted were 

 Pteromali, which are known to attack the eggs of 

 insects. 



Cliaitopliorus aceris is plentiful throughout the year 

 on the maple, Acer pseudoplatanus, on the sycamore, 

 A. 'platanoides, the field-maple, A. campestre, and the 

 Montpellier maple, Acer MonspelUensis. Mr. Walker 

 told me that he also took it feeding on the horse-chest- 

 nut, JEsculus parviflora. 



Both the winged and apterous viviparous forms 

 may be seen under the leaves throughout the summer ; 

 and, as the parents scarcely move from the spots where 

 they deposit their young, they are usually surrounded 

 by them to the number of twenty, or Walker says 

 " hundreds." These young, which are green and 

 hairy, have mostly their heads turned towards a com- 

 mon centre, and in this manner circular patches are 

 formed. Walker says that these young remain in the 

 same place, and without further growth, for three 

 months, and that they do not begin to increase in size 

 till the September following. 



It remains now to consider the extreme dimor- 

 phous form of this singular Aphis, which, as far as we 

 know, has no trace of sexuality, and is wholly unable to 

 reproduce its kind by gemmation or otherwise. 



On Dimorphism in Ohaitophorus aceris. 



The world-wide interest that has been evoked by 

 the writings of Mr. Darwin has certainly had one 

 beneficial influence, viz. that of compelling thinkers 

 to regard biological phenomena from more than one 



