66 BRITISH APHIDES. 



Prumos armeniaca. To these plants I would add the 

 chrysanthemum and the china-aster. Probably the 

 winged female determines the kind of food for the 

 sustenance of her future progeny, which has no op- 

 portunity of exerting a choice in the matter. 



Ajjhis jyruniis exceedingly destructive. Multiplica- 

 tion takes place by millions, and the insects close up 

 the pores of the leaves by their tenacious secretions 

 and the mealy exudations from their bodies. By the 

 constant irritation of their rostra the leaves roll up, 

 and under this cover from the weather both the 

 winged and apterous forms live, ovierspread by the 

 before-mentioned mealy powder, which probably to 

 them is a protection. 



De Geer describes the male as having wings hardly 

 as long as the body, and the female as laying her eggs 

 in September. Professor Asa Fitch has noticed the 

 discordant descriptions of this A23his, and is led to 

 believe that the American plum Aphis is distinct from 

 the European. The English species certainly is vari- 

 able, both as to the length of the antennte and the 

 forking of the cubital vein. Some winged forms have 

 but six antennal joints, but doubtless this condition is 

 abnormal. 



Notwithstanding differences in Kaltenbach's dia- 

 gnosis, I do not doubt that the German and English 

 specimens are identical. 



I am inclined to believe that Aphis primifoliiB of 

 Fitch is a variety of A. ]_)runL In both insects the 

 nectaries of the winged female project beyond the 

 tail. 



The china-aster of our gardens is very liable at some 

 seasons to entire destruction by an Aphis which 

 swarms round the flower-stalks, and forms thereon a 

 dark living crust. Where the Aphis frequents, it 

 causes black blotches, which afterwards spread over 

 the plants and cause them to rot ofi". With the 

 single difference (which, however, is of some conse- 

 quence), viz. that this Aphis does not appear to have 



