KEY TO CLASSES AND ORDERS OF ANIMALS 2i 



Phylum ARTHROPODA 



1(14) With one pair of appendages in front of the mouth. 

 (Either cheUcerae adjacent to the anterior border of 

 the mouth or antennae some distance in front of it.) 

 The antennae in some larval forms are reduced to mere 

 jointed tubercles. Body usually differentiated into 

 head and trunk. 2 



2(5) Without distinctly jointed appendages on the trunk, 

 often with unjointed appendages. 3 



3(4) Trunk distinctly segmented. 



Class Insecta larvae, p. 37 



4(3) Trunk not distinctly segmented. Trunk appendages 

 stumplike and ending in two claws. (Pratt, 462.) 



Class and order Onychophora 



5(2) With distinctly jointed appendages, legs, on the 

 trunk. 6 



6(7) With more than four pairs of legs. 



Class Myriapoda, p. 27 



7(6) With two, three or four pairs of legs. 8 



8(9) With one or two pairs of wings used in flight or at 

 least capable of free movement, or with the first pair 

 of wings in the form of thickened wing covers (elytra) 

 meeting in a straight line down the middle of the back 

 and sometimes fused. 



Class Insecta, winged adults, p. 30 



9(8) Wings absent or represented by immovable rudiments. 



10 



10(11) With three pairs, or rarely, with two pairs of legs. 

 Head, thorax, and abdomen usually distinct. Worm- 

 like or grublike forms, quiescent or active or forms 

 resembling adult insects. 



Class Insecta (young, i.e., nymphs, larvae, pupae, and 

 a few wingless adults). p. 34, 37, or 42 



