21 



The Maple Aphis and its Dimorphic Larva. 



By E. J. BuNNETT, M.A. Head May 27th, 1915. 



The Maple Aphis, to which the name Chaitophoras aceris was 

 given by Linnjeus, occurs, according to Buckton, in the following 

 various forms : — 



(i) An a}iterous viviparous female, some of which are green and 



others entirely black, 

 (ii) A iiin(/ed cirijiaruns female, some bright green, others slightly 



larger and shining black, 

 (iii) The jmpa with green wing-cases and otherwise very similar 



to the apterous viviparous female, 

 (iv) An oviiiarons apterous female which is said to deposit its eggs 



in November and December, 

 (v) llie males, which occur in two forms simultaneously, some 



apterous and some alate. 

 This Maple Aphis may be found plentifully on various species of 

 Acer in this country, e.fi.: — 



A. pseudoplatantis (Sycamore), 

 A. jilatanoides (Norway Maple), 

 A. campestre (Field Maple), 

 A. monspessulaniDii (Moatpelier Maple), 

 A. negundo (Box-elder), 

 on all of which I have taken it myself. 



There are two forms of the young which appear simultaneously, 

 the one normal ; the other, the curious form which was described 

 in 1852 by Thornton and named by him Pht/llophorns testndinatiis. 



In 1858 Lane Clark observed it and gave it the name of Chely- 

 morpha testudu. 



Four years later Van der Hoeven described it under the name of 

 Periphyllus testiido. 



So far all had agreed in regarding this strange little insect as the 

 larva of some unknown aphis. 



In 1867 Balbiani and Signoret published an engraving of the 

 dimorphic larva and stated that the same green viviparous female 

 of Chaitophoras aceris individually produced both the normal and 

 abnormal larval forms. 



The live specimens exhibited at this meeting including 26 of the 

 dimorphic larvfe on a single leaf of pseudoplatanus are the first I 

 have found this season. 



