PEMPHIGUS BUESARIUS. HO 



Kocb. was aware that these habitations were the 

 work of the stem-mother. 



Notwithstanding the concealed hfe of these insects, 

 they are by no means secure from the attacks of 

 enemies. Minute A]yliidivoroiis IchneumonidcB succeed 

 in introducing their eggs, and the larvse from these 

 destroy the inhabitants and speedily cause the break- 

 ing up of the gall. After the galls are vacated they 

 form a nidus for a small fungus which speedily con- 

 verts them into dry dust. 



M. Lichtenstein obligingly forwarded me in July 

 excrescences from the Poplar, which rise from the 

 more woody portion of the twig. Though constructed 

 almost side by side with the pyriform galls, they differ 

 much in form, being more spherical and rugose on 

 their surfaces. 



M. Lichtenstein, partly from these differences, 

 hesitates to accept the pear-shaped construction as 

 the work of P. bursarius. I am not aware that he has 

 yet published any memoir on the specific differences 

 of the insects fabricating these two descriptions of 

 galls, but he suggests to me that the woody spherical 

 gall is the work of P. bursarius, smd. that the pear-shaped 

 excrescence is fabricated by an undescribed species, 

 for which he proposes the name of P. injriforT^iis. 



Reaumur gives a good woodcut of a sprig of poplar 

 on which five galls are represented, two rising from 

 the stem, two from the petioles of the leaves, and one 

 from the midrib.^' These he distinguishes in his 

 description of the figure thus : — " La figure represente 

 un bout de branche de peuplier charge de plusieurs 

 feuilles ; galles que partent des pedicules des feuilles 

 (P. lyijriformis, Licht.), autres galles qui tirent leur 

 origine immediatement de la tige (P. bursarius^ Licht.), 

 et une galle d'une feuille (P. marsupialis).^^ Reaumur 

 groups these as the work of a single species, and I 

 believe all authors up to the present time have simi- 

 larly regarded the question. 



* Reaumur, 1. c, t. Hi, pt. xxvi, fig. 8, 



