106 



FIRST BOOK OF ZOOLOGY. 



Some of the nuts will be empty, because the gall-insects 

 have already escaped. 



Galls are also produced by insects not at all like the ich- 

 neumon. The following figure, which represents a gall com- 

 mon on the golden-rod, is produced by a two-winged fly. 

 The figure represents the stem or stalk unnaturally swollen, 

 the swollen portion being the gall, within which the larva, 

 pupa, or perfect insect, may be found if the creature has not 

 already escaped. 



FIG. 103. GALL ON GOLDEN-HOD STALK. p, Pupa removed from the Gall. 



Let the pupils arrange in their collecting-box a leaf with 

 the nut attached, a nut cut open showing the pupa-case, and 

 the insect pinned. 



97. Only a few brief lessons have been given represent- 

 ing the life-history of a butterfly, mud- wasp, mosquito, spit- 



