54 WALTER N. HESS. 



and moss. In confinement, at the insectary, oviposition was 

 observed on several occasions. The female walked slowly over 

 the soil, thrusting out her long ovipositor into the depressions in 



the earth, where the light yellowish eggs 

 were deposited. Eggs laid by these 

 females were usually deposited singly, 

 though sometimes in masses. Some were 

 placed from one eighth to a quarter of 

 an inch underneath the surface, others 

 on the surface, and some were deposited 

 on the roots, basal stems and leaves of 

 moss and grass. The egg (Fig. 6) is 



FIG. 6. Photurus pennsylva- 



nicaegg. small, nearly spherical, about .7 by .8 



mm. in diameter. It is without surface 



markings, though at the time of laying it is covered with an 

 adhesive surface. 



It is frequently stated in literature that the eggs of fireflies 

 are luminous, and Williams (1917) states that the eggs of this 

 species glow when deposited and probably continue to emit light 

 until the time of hatching. The certainty of this statement 

 seems in doubt. At the time of laying, the eggs were found to 

 be very slightly luminescent for a period of two days, but in no 

 case did they, at this period nor until the light-organs of the 

 larva were developed, definitely emit light. Eggs removed 

 from the ovaries of a ripe female showed no evidence of luminosity, 

 though Williams thought he saw a light in some of the eggs 

 that he so removed. Fabre (1913) states that the eggs are lumin- 

 ous even before leaving the body of the mother, but this seems 

 very much in doubt. The so-called luminescence of the eggs 

 at the time of laying is probably due to the substance with which 

 they are covered, rather than to any internal property of their 

 own, and as this becomes dry the slight luminescence disappears. 

 At a period about four days before the eggs hatch the larval 

 light-organs become functional, and from this time until hatching, 

 the eggs emit a distinct light. 



In the breeding cages at the insectary where normal outdoor 

 conditions were maintained, the eggs of this species hatched in 

 from twenty-five to twenty-seven days, depending on weather 



