120 BRITISH APHIDES. 



Kirby and Spence long ago spoke of " Aphis hur- 

 sarla, wliicli, with its brood, inhabits augula.r utriculi 

 on the leaf-stalk of the black poplar, numbers of which 

 I have observed on the trees by the roadside from Hull 

 to Cottingham." Kaltenbach says, '" Die Gallon sind 

 an den verschiedenen Stellen auch verschieden gebil- 

 det." The following is the substance of his remarks 

 on P. hursarius. The galls are differently constructed 

 in different situations. The stem-mother which has 

 survived the winter forms a swelling on the leaf-stalk 

 (Blatt-stiel), which quickly rising on all sides forms a 

 kind of groove in which the insect lies. The edges of 

 this cavity draw themselves together over the creature, 

 and at last wholly close her in. Sometimes two 

 females work on the same foot-stalk, and their com- 

 bined action modifies the form of the gall.* Koch 

 gives two positions for the gall, one is constructed, he 

 says, on the midrib of the leaf, and the other less fre- 

 quently on the ends of the leaf- stalk ; in these galls the 

 openings are found at the sides : " Seltener bilden sich 

 am Ende der Blatt-stiele solche Blasen." Passerini 

 says : — " Intra gallas petioli et costee foliorum Pojmli 

 nigne, Maio, Junio, et serins in gallis terminalibus 

 ramuorum ejusdem speciei."t 



I have compared the inhabitants of both galls, but 

 although I see a difference in size of the insects, and a 

 modification of the ringing of the fifth antennal joint, 

 I do not feel competent to decide from these characters 

 that they belong to different species. M. Lichten- 

 stein's experience in these special genera will doubtless 

 set the point at rest in one of the future papers he has 

 promised on the Pempliigians. As the pseudo-gall 

 itself is characteristic, I have figured it for the pur- 

 pose of drawing the attention of British entomo- 

 logists, yet still provisionally retaining it as constructed 

 by P. hursarius. 



* Kalt., ' Mou. der Pflanzenlause, p. 183. 

 f Pass., ' Aphid. Italicse,' p. 75. 



