MOUTH PARTS OF THE NYMPH. 



Text-figure I. 



Types of May-fly Mandible. 1. Baetisca, molar surface removed. 2. Lep- 

 tophlebia, molar surface removed. 3. Siphlurus, molar surface removed. 

 4. Epeorus, inner canine. 5. Heptagenia, outer canine. 6. Ecdyurus, outer 

 canine. 7. Epeorus, outer canine. 8. Caenis, all tips removed. 9. Calli- 

 baetis, molar surface removed. 10. Blasturus, molar surface removed. 11. Iron, 

 outer canine. 12. Pentagenia. 13. Tricorythus, molar surface removed. 

 14. Hexagenia, molar surface removed. 15. Chirotenetes, outer and inner canine. 

 16. Iron, canines. 17. Ephemera, molar surface removed. 18. Callibaetis, 

 canines and Iacinia. 19. Atneletus, outer canine. 20. Ephemerella, molar surface 

 removed. 21. Euthyplocia, tusk and canines. 22. Baetis, canines and Iacinia. 

 23. Potamanthus, molar surface removed. 24. Polymitarcys, molar surface re- 

 moved. 25. Blasturus, canines and Iacinia. 



Among the exotic genera are some rather aberrant forms. In the nameless 

 Chilean nymph figured by Eaton (PI. IV, fig. 63, c), the canines are extremely 

 well developed, and certainly suggest carnivorous habits. This region in Palin- 

 genia (fig. 49, c) is not distinctly differentiated. Lachlania (fig. 56, c) possesses 

 but one canine on the mandible, and that is no longer apical in position. The 

 canines of Homeoneuria (fig. 62) and Lachlania are covered with scale-like teeth. 



Hypopharynx (PI. V). 

 The hypopharynx of May-fly nymph is a relatively large tongue-like process 

 at the dorsal base of the labium. As with the labrum, the chief variations are in 

 the form of the anterior border. The free edge of the median lobe of Atneletus 



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