OUTLINES OF ENTOMOLOGY. 47 



also burning the stubble is the best preventive of their increase. This 

 fly dififers very slightly in structure fron the parasitic species. 



One family included in this group — the Cynipidal — while resem- 

 bling the Chalcids very closely in structure, are vegetable feeders, 

 causing on Oak, Eose and other woody plants, the singular fruit-like 

 and nut-like growths called " galls." The females differ from the para- 

 sitic Chalcidid^ in their larger size, and in the shorter and more 

 compressed abdomen and in the notch on the under side of the latter. 

 The antennoe, also, are straight and slender, with the joints all equal. 



The abnormal plant growth is supposed to be caused by the depo- 

 sition of a minute quantity of a peculiar fluid, along with the egg, by 

 the parent fly, the tissue resulting forming a more suitable kind of 

 food for the larvae than ordinary wood fiber or leaves. The gall makers 

 are all more or less injurious to the plants they attack, but one species 

 makes a sort of reparation in producing on a European oak the " nut 

 galls," used in the manufacture of the best ink. 



CHAPTER XIII. 



Order HYMENOPTEKA.. Section Terebrantia. 



SAW-FLIES and HORN TAILS. 



[Fig. 21.] 



Native Currant Saw-fly. 



Colors— (a) gre3ii and black ; (b) black and honey -yellow. 

 Native C arrant-worm— Pn's?ojj/(ora grosw/arioi^after Riley. 



The insects of this Order, included among the true Plant-eaters 

 (Phytophaga), differ very much in all stages of their development from 

 those described in preceding chapters. 



The perfect insects have rather heavy bodies, upon which the three 

 principal divisions are not so distinct as in bees, wasps and ichneu- 



E — 4 



