20 
INSECTS. 
Tho phenomenon known as the alternation of generations,—that is to say, 
where produced generations alternate with each other in consecutive succession,— 
1 , common oak-gall wasp; 2, Torymus regius, a parasite on the same; 3, Gall of Cynijos gemmce ; 4, Larval 
chamber, shut and open ; 5, The same enlarged, above on the left is figured the purple hairstreak and its 
larva; 6, The same enlarged ; 7, A gall cut through, showing the grub. 
1, the sponge gall-wasp, with an old sponge-gall; beneath is a new gall, whence the wasps have not yet made their 
exit; 2, oak-root gall-wasp, with its gall; 3, bramble gall-wasp ( Diastrophus rubi), with its gall ; 4, A gall of 
the same slit in half; 5, Synergies facialis ; 6, Figites scutellaris, parasites; 7, Ibalia cultellcctor, parasitic on 
Sirex juvencus. (All the galls and Fig. 7 nat. size ; Fig. 6 enlarged.) 
