Galls caused by the queen and nymphs ot Pemphigns 

 spirothecae Koch. 



on 



the petioles of leaves of Populus nigra Linn. 



PLATE 105. 

 Synonymy of Insect. 



Pemphigus affinis Koch. 



„ spirotheccE Pass., Kerner. 



Puceron de peuplier Reaumur. 



Habitat of the Black Poplar. — Common in most parts 

 of Britain in woods, gardens, and parks, along the banks 

 of rivers and streams and other moist places. 



The G.\ll is formed by the queen aphis puncturing the 

 petiole of the leaf, causing it to assume a spiral form, 

 within the cavity of which she becomes immured. 



Position.— On the petiole of the leaf. 



Manner of Growth. — Singly ; glabrous ; spiral and multi- 

 reniform in shape. 



Colour. — Slightly darker green than other portion of the 

 petiole. 



Average Dimensions of a Mature Specimen. 

 Length, 8 mm. ; girth, 30 mm. 



May be sought during the months of June, July, August, 

 and September. 



The Growth is complete by the end of August. 



The Typical Condition of the gall is multinymphal. 



ECDYSIS takes place in the gall. The imagines emerge during 

 August. 



Pemphigus spirothecce appears to be very local and exclusive 

 in its habits. Among several poplars near each other, one only 

 may be attacked, the others showing no signs of gall-growths. 



The gall is also figured by Buckton, "Briti.sh Aphides," 

 vol. iii., plate 112; A. Kerner, " Nat. Hist, of Plants," vol. ii., 

 P- 531- 



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