20 Journal New York Entomological Society. [Vol. xm. 



Fig. 7. T. plastographus. Cross-section of wing well evaginated, showing 

 threadlike bases of cells and tracheoles well developed. 



Fig. 8. T. plastographus. Cross-section of wing through a vein cavity, show- 

 ing wing extending to base of leg bud. 



Fig. 9. T. plastographus. Cross-section of wing, showing beginning of folding 

 of wing and the pulling of the nuclei into one row. Trachea; and tracheoles in the 

 vein cavities. 



Fig. 10. T. plastographus. Cross-section of part of wing from same larva as 

 Fig. 9, showing elongated bases of cells and trachese and tracheoles in vein cavity. 



Fig. 11. T. plastographus. Full grown wing, shortly before pupation. 



Fig. 12. T. plastographus. Cross-section through the metathoracic spiracle. 

 (The cuticle was pulled away from the hypodermis during sectioning.) 



Fig. 13. T. plastographus. Tracheole from full grown wing. 



Fig. 14. 7\ plastographus. Tracheoles formed around the nuclei, from base 

 of wing just before second moult. 



Figs. 15 and 16. T. plastographus. Tracheoles from prepupal wing. 



Fig. 17. T. plastographus. Bundle of tracheoles entering wing. From larva 

 in prepupal period. 



Fig. 18. Just starting wing disc of a Buprestid. 



Fig. 19. Wing disc just beginning to evaginate, showing great proliferation of 

 tracheoles. From same Buprestid as Fig. 18. 



Fig. 20. firuchus sp. Cross-section of wing well evaginated, showing trachea 

 in vein cavity and the thick walls of the wing bud. 



Fig. 21. Bruchus sp. Wing at a later stage than Fig. 20. The basement 

 membrane has nearly degenerated. 



Fig. 22. Dendroctonus valens. Full-grown wing shortly before pupation. 



p'ig. 23. D. valens. Forming wing disc, just before last moult, showing folding 

 of the disc and the tracheoles at base. 



Fig. 24. Ozognathus cornutus. Lateral tracheal system from a larva cleared 

 in cedar oil. 



Fig. 25. Thymalus marginicollis Chev. Lateral view of front part of body of 

 a full-grown larva, showing metathoracic spiracle. 



Fig. 26. Lateral view of meso- and metathorax of a larva of an Erotylid, show- 

 ing meso- and metathoracic spiracles and their positions. 



Fig. 27. Bombyx mori. Lateral view of larva just after second moult, cleared 

 in cedar oil, showing lateral tracheal system of thorax, the vestiges of the metathoracic 

 spiracle and the wing discs. 



Fig. 28. Apis mellifica. Lateral view of head, thorax and first abdominal seg- 

 ment, showing the leg and wing buds as seen through the cuticle, and their relation 

 to the spiracles. From larva one half grown, cleared in cedar oil. 



Fig. 29. Apis mellifica. Larva (prepupal period early) showing relative posi- 

 tions of spiracles and wing buds, as seen through the cuticle. 



Fig. 30. From same larva as Fig. 29. Ventral view showing wing and leg 

 buds. 



Fig. 31. Tomicus plastographus. A not quite cross-section of a larva just be- 

 fore last moult, showing hinder margin of metathoracic wing disc and part of first 

 abdominal spiracular trunk, to illustrate the relative heights on the pleurum of the 

 spiracles and wing discs. 



