CHAPTER XVIII 



THE FOOD OF ANIMALS— PLANT-EATING INSECTS AND 



MYRIAPODS 



The enormous Phylum of Arthropoda embraces an extra- 

 ordinary variety of species, which play the most diverse parts 

 in the economy of nature. It will be convenient, as before, to 

 deal first with the Insects and other air-breathing forms and 

 then with the Crustacea and their allies. 



INSECTS (Insecta) 



It has already been explained (see p. 102) that Insects 

 possess three pairs of jaws, which are adapted for biting, pierc- 

 ing, or sucking, as the case may be, and by means of these 

 plant food can be attacked as well as that of animal nature. 



The following nine orders are recognized: — 



A. — Insects with biting mouth-parts (in the adult). 



1. Membrane-winged Insects (Hymenoptera). — ^Bees, Wasps, Ants, &c. 



2. Beetles (Coleoptera). 



3. Net-winged Insects (Neuroptera). — Dragon-Flies, May-Flies, &c. 



4. Straight-winged Insects (Orthoptera). — Cockroaches, Locusts, &c. 



5. Wingless Insects (Aptera). — In some of these the mouth may be 



imperfectly suctorial. 



B. Mouth more or less perfectly suctorial (in the adult). 



6. Scale-winged Insects (Lepidoptera). — Moths and Butterflies. 



7. Flies (Diptera). 



8. Fringe-winged Insects (Thysanoptera).— Corn-Thrips, &c. 



9. Bugs (Hemiptera). 



MEMBRANE-WINGED INSECTS (Hymenoptera) 



Saw-Flies. — The first insects to be here considered are Saw- 

 Flies and their allies, distinguished by the absence of the "waist" 

 so characteristic of wasps and the other members of the order. 



