EXPLANATION OF PLATES. 



List of Abbreviations. 



A. — anal vein. 



a. — anus. 



ac. — axillary cord. 



ant. — antenna. 



ap. — apodeme. 



asc. — accessory sclerite. 



cl. — clypeus. 



Cu. — cubitus. 



ex.— coxa. 



e. — eye. 



epm. — epimeron . 



eps. — episternum. 



/. — frons. 



fp. — forceps (male). 



fu. — furcae. 



g.—geua.. 



gc. — genal cone. 



lab. — labium. 



labr. — labrum. 



M. — media. 



mc. — meracantlius. 



mn. — mandibular seta. 



mx. — maxillary seta. 



o. — ocellus. 



P. — pronotum. 



p. — penis. 



Psc. — praescutum (doreulum). 



pt. — parapteron. 



ptb. — preocular tubercle (Livia.) 



PN. — Pseudonotum. 



R. — radius. 



Rs. — radial sector. 



S. — sternum. 



Sc. — subcosta. 



Scl. — scutellum. 



sp. — ^spiracle. 



tn . — trocbautin . 



V. — vertex. 



■w. — wing. 



ivp. — wing process. 



Plate 1. 



[ Structure of skeleton.] 

 Fig. 1. Arytaina robusta, lateral view showing sclerites of bead and thorax. (See 

 above for explanation of abbreviated terms.) Stippled areas are conjunc- 

 tival membrane. Dotted lines indicate endoskeleton. 



2. Apsylla dstellata, lateral ^dew of thorax. Compare metathorax with, that 



of (1). 



3. Livia vernalis, lateral view of head and thorax. 



4. Psylla alniamericana, lateral Yie\Y of thorax. 



5. Psylla pyri, cephalic view of head, showing the sclerites and suppression 



of the frons. 



Plate 2. 

 [ Structure of skeleton.] 



6. Euphyllura arbuti, sclerites of thorax. 



7. Trioza albifrons, same. 



8. Psylla pyricola, same, -with base of abdomen, also. 



9. Apsylla dstellata, ventral view of head and thorax. 



10. Psylla alni americana, metacoxa, metafurcee, part of epimeron, metasternum 



and chitinous process from metafurcte connecting the endoskeleton with 

 the inner surface of the exoskeleton. The episternum and most of the 

 epimeron is removed. 



11. Same, caudal view. 



12. Apsylla dstellata, caudal \dew of metathorax, partially diagrammatic, show- 



ing comparatively simple metafurcse. 



Plate 3. 

 [ structure of skeleton.] 



13. Psylla pyricola (male), lateral \dew of abdomen, distended, showing segments, 



spiracles, and atrophied and modified sclerites. 



14. Same, female. 



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