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EXPLANATION OF THE FIGURES. 



Fig. 1. Caterpillar-sac of Psyche Helix, Sieb., seen from the side. 

 Natural size, b, opening which has been left by an escaped 

 Chalets. 



Fig. 2. The same sac with the caterpillar; a, aperture which the 

 caterpillar always leaves in this spot during the enlargement 

 of its sac. 



Fig. 3. The same sac seen from above ; a, as in the preceding figure. 



Fig. 4. Full-grown caterpillar of Psyche Helix. Natural size. 



Fig. 5. Female pupa of Psyche Helix. Natural size. 



Fig. 6. Sac with caterpillar of Psyche Helix. Enlarged. «, as in 

 fig. 2. 



Fig. 7. Caterpillar of Psyche Helix. Enlarged. 



Fig. 8. Maggot-like female of Psyche Helix. Natural size. 



Fig. 9. The same enlarged. By transmitted light the urinary vessels 

 appear black under the microscope, and not yellowish-white 

 as by direct light, c, head ; d, a portion of the urinary 

 vessels shining through the integument. 



Figs. 10, 11, 12. Three figures copied from Reaumur 's Memoir es, 

 torn. hi. pi. 15. figs. 20-22. Enlarged sacs of Psyche Helix, 

 which Bazin found upon sandstone in the vicinity of the 

 Hermitage d'Estampes. 



Fig. 13. Chalcis nigra, Koll., from Psyche Helix. Natural size. 



Fig. 14. The same insect enlarged. 



Fig. 15. Caterpillar-sac of Psyche Planorbis, Sieb., seen from above. 

 Natural size. a, spot in which the walls of the sac are 

 deficient, as in fig. 2. 



