KEY TO PHYLA 19 



10. (7) Two pairs of wings similar, membranous n 



ii (12) Last joint of the tarsi bladder-like or hoof-like in 

 form and without claws ORDER PHYSOPODA 



12. (11) Last joint of tarsi not bladder-like 13 



13. (14) Wings entirely, or for the greater part, clothed 

 with scales. Mouth parts for sucking ORDER LEPIDOPTERA 



14. (13) Wings transparent and naked or thinly clothed with 

 scales ~ - 15 



15. (16) Mouth parts a jointed tube for sucking, arising 

 from hinder part of ventral surface of head 



_ ORDER HEMIPTERA (Homoptera) 



16. (15) Mouth parts not united to form sucking beak. 

 Wings net veined with very numerous veins and cross veins 17 



17. (24) Tarsi of less than five segments 18 



18. (21) Antennae inconspicuous, awl-shaped, short, slen- 

 der 19 



19. (20) First and second pairs of wings of nearly the same 

 length. Tarsi three jointed ORDER ODONATA 



20. (19) Second pair of wings either small or wanting. Tarsi 

 four jointed ORDER EPHEMERIDA 



21. (18) Antennae usually conspicuous 22 



22. (23) Tarsi two or three jointed. Second pair of wings 

 broader at base than first pair or at least as large as the first 



pair ORDER PLECOPTERA 



23. (22) Tarsi four jointed. Wings equal in size 



. ORDER ISOPTERA 



24. (17) Tarsi with five segments. Abdomen with hair-like, 

 many jointed, anal filaments ORDER EPHEMERIDA (in part) 



25. (6) Wings wanting, or in some cases represented by im- 

 movable rudiments, the wing pads 26 



26. (27) With typically three pairs of legs. Head, thorax, 

 and abdomen usually distinct ; head always distinct. General body 

 form resembling that of adult insects. CLASS INSECTA (nymphs, 

 larvae, pupae, and a few wingless adults) 28 



