66 



WALTER N. HESS. 



although they do not shine with a bright luminescence unless 

 the pupa moves, or is disturbed (Fig. 16). 



The head, thorax, and even the abdomen of the pupa, as well 

 as the newly emerged adult, have been described as luminous 

 (Williams, 1916). It must be admitted that the entire insect 

 appears faintly luminous at these periods, but the cause for it 



LO - 



LO 



FIG. 16. FIG. 17. , 



FIG. 16. Photurus pennsylvanica pupa, ventral view of abdomen. LO, larval 

 light-organ. 



FIG. 17. Same as Fig. 2, except taken one day after emergence when larval 

 light-organs (LO) were still visible. AO, adult light-organ. 



seems to be due more to the light of the abdominal light-organs 

 shining through the non-pigmented coverings of the insect's 

 body, than to the luminosity of the fat or other internal struc- 

 tures. A freshly molted larva appears much the sam. as the 

 two stages refened to above. 



The date of pupation for this species, at Ithaca, New York, 

 ranges from May 20 to June 15, depending largely on the season. 



