PLATE 3 



EXPLANATION OF FIGURES 



9 Photuris pennsylvanica larva, first instar. 



10 Photuris pennsylvanica larva, full-grown. 



11 Photuris pennsylvanica pupa, ventral view. 



12 Photuris pennsylvanica larva, full-grown, ventral view. P, photogenic 

 organ; S, spiracle. 



13 Cross section of photogenic organ of full-grown larva of Photinus con- 

 sanguineus. B, blood cell; C, cuticula; //, hypodermis; .1/, muscle; N, nerve; 

 P, luminous layer; T, trachea; U, urate or reflector layer. 



14 Sagittal section of photogenic organ of embryo Photuris pennsylvanica. 

 A, fat cell; H, hypodermis; M, muscle; P. luminous layer; T, trachea; U, urate 

 or reflector layer. 



15 Sagittal section of photogenic organ of embryo Photuris pennsylvanica, 

 an earlier stage of development than in figure 14, A, fat cell; //, hypodermis; 

 M, muscle; O, light-organ; T, trachea. 



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