NOTES ON THE BIOLOGY OF THE FIREFLIES. 



Walter N. Hess. 



(DcPanw TTuivorsHy.) 



Duriiiff the past yoar I Itocaine inlerostod in studyiiij,' (ho lii()hif,'y of tlie 

 firoflios. and after lookins up the literature on the gronji I concliided that 

 little was known rej^arding Iheni except what had heen learned from a study 

 of the adults. 



The following species were studied: I'Jiothius coiixani/iiincus Lee. 7'7io- 

 tinus scintillans Say, Photurus pcnnsylvanicus DeGeer, and Pyropyga fcne- 

 stralis Mels. Most attention, however, was given to Photiirus pcnnsyl- 

 ranicu, and this paper will he limited to a discussion of that species. 



This firefly, Photunis pen ns i/l rani ca, is one of the largest and most 

 common of our native species. As is common of our luminous fireflies, 

 the adults are usually found only at night since they siKMid the day con- 

 cealed underneath moss or grass, although occasionally si)ecimens were 

 found clinging to the underside of leaves of low vegetation. Like many 

 other insects, this species has well defined centers of distribution, it being 

 rarely found except along marshy or moist localities. Some of the smaller 

 species of fireflies, however, seem to prefer the drier regions. 



Many insects during their adult life eat little or no food, but the adults 

 of this species, especially the females, are very voracious in their feeding 

 habits. These females were commonly observed devouring other species of 

 fireflies, and uot infrequently the males of their own species. 



In the case of nearly all our luminous fireflies the female never flies, but 

 remains on or near the ground and there awaits her mate. In this species, 

 however, the female is also an active flier. 



It is agreed by most students of fireflies that the light-emissions serve 

 to bring the two sexes together. In our smaller native species there is 

 a definite interchange of flashes, by which the male is able to find the 

 female. In this species both sexes are active fliers and they flash frequently 

 whether in the presence of each other or not. In no case was there observed 

 a definite exchange of flashes between the sexes of this specie.s. Yet. on 

 several occasions while holding females in my hand, male.s flew to them, 

 and on two occasions while holding males, females flew and alighted be- 

 side the captured males. This would lead one to believe that there is a 

 definite sexual attraction between the sexes of this species, and that the 

 females having become active fliers, are also attracted to the males. 



The characteristic place for the oviposition. by the females, is at the base 

 of grass or moss in damp loamy soil. The eggs which are deiiosited about 

 the first of June are usually placed in little cracks or depressions in the 

 earth, and there they remain for a period of approximately 2<; days, when 

 they hatch into little larvae. These little larvae, which hatch altout .July 

 first, require nearly two years to conqtlete their L'rowlh licforc they trans- 

 form into adults. 



The larvae resemble to a considerable extent the habits of the adults as 

 they are active only at night. This makes it rather ditticult to study their 



