525 



lice, when the slit on the upper side of the leaf, through which 

 the mother plant-louse built up the gall early in the spring, 

 gapes open and allows 

 the insects to escape 

 into the open air." 

 (American Entomolo- 

 gist, p. 108.) 



The Editors of the 

 "American Entomolo- 

 gist" describe and fig- 

 ure the Apple root 

 plant-louse, Eriosoma 

 (Pemphigus) pyri of 

 Fitch (Fig. 526 ; a, the 

 gall ; 5, larva ; c, fe- 

 male ; d, leg ; e, beak ; 



/, antenna of female ; Fig. 52 1. 



#, of larva), which occurs sometimes in great abundance, form- 

 ing, in October, galls like potatoes, and two to three inches in 

 diameter, on the roots of apple trees, just beneath the surface 

 of the ground. 



The European 

 Chermes (Pemphi- 

 gus) abietis has two 

 sorts of females, 

 and is parthenogen- 

 ous, according to 

 Leuckart. 



Fig. 525. 



Fallen. 

 The Bark-lice have 

 six or. more joints 

 to the antennae ; the 



tarsi are two-jointed, the beak wanting in the males, in which 

 the hind wings are usually wanting, while the scales made by 

 the females are usually flattened, scale-like, or rounded hemi- 

 spherical. The wingless, scale-like, adult females, by a retro- 

 grade development, in which the legs and rings of the body 

 become aborted, remind us of the Barnacles and allies among 



