122 BRITISH APHIDES. 



the same assiduity as he has clone. In many parti- 

 culars he can speak with more authority on a group 

 which he has made his speciality. 



o.. 



Pemphigus spirothece, Kocli. Plate CXI, figs. 8 — 9 ; 

 and Plate CXII, figs. 1—6. 



Fenq^higus affinis, Koch. 

 Pemphigus sjpirothecce, Pass; 

 . Puceron de peupUer, Reaumur.* 



Apterous viviparous female. 



Incli. Millimetres. 



Size of body 0-060xO-030 l-52xO-76. 



Length of antenna 0-030 0-76. 



Elliptical, wholly pale green or yellowish ; very 

 lanuginous. Antennse short, formed of four joints only ; 

 but a constriction of the third joint shows a tendency 

 to develop another joint. Eyes very small; rostrum 

 reaches to the second coxes. The abdomen and legs 

 clothed with cotton-like tufts. 



]} I have never met with the winged form of P. spiro- 

 thecce, but Koch figures it apparently under the name 

 P. affinis ; and Passerini describes it as being very like 

 the imago of P. hursarius. The fourth wing-nerve 

 rises from a point scarcely beyond the half length of 

 the stigma. The former species may be distinguished 

 from the latter by the abundance of woolly matter 

 which clothes the apterous form of P. spirothecce. 



The covered dwelling of this species is formed by 

 the Queen Aphis, by puncturing one side of the leaf- 

 stalk of the poplar, most usually that of Populus nigra. 

 This irritation causes the stalk to flatten and, curve 

 itself into an elastic spiral, the edges of which press 

 ao-ainst each other, so as to form a chamber, in which 

 the species multiplies and undergoes pupation. 



* ' Mem. des Insectes,' t. iii, pi. 28, figs. 1 — 4. 



