PAPERS ON PSYCHOLOGY AND PHY'SIOLOGY 109 



A POSSIBLE IXTEEPEETATIOX OF THE SYX- 

 CHEOXOUS FLASHIXG OF FIREFLIES 



ChKISTIAX a. ErCKMICK, L'XITEESITY OF IlLIXOIS 

 I. THEOEETICAL AND HISTOKICAL 



Lumiiiescence iii living organisms has rarely failed to 

 excite the curiosity and vi'onder of mankind. The rec- 

 ords of travellers and explorers frequently contain ac- 

 counts of various forms of the phenomenon and of its 

 presence in many dilferent varieties of animal life. 

 There have also appeared from time to time a large num- 

 ber of scientific descriptions and explanations relating 

 to the biological function, the chemical production, and 

 the characteristic conditions of its occurrence. In 1910 

 Mangold (18)^ was able to collect 649 titles on the sub- 

 ject and in the last decade several scores of additional 

 contributions must have appeared. We are not here con- 

 cerned, however, with the general subject. Some con- 

 siderations, like the biological function of the phenome- 

 non and the chemical nature of it, may have important re- 

 lations to the discussion but time forbids a more detailed 

 examination. Suffice it, then, to remark that among in- 

 sects it is claimed, first by Osten-Sacken (23), then by 

 McDermott (17) and Mast (19), that luminescence is very 

 likely a secondary sex characteristic, especially so in the 

 fireflies (Lampyridae). Recently Harvey (12) has also 

 reported on the chemical changes that take place during 

 the flashing. 



But we are chiefly interested in the problem of the con- 

 certed beha^'ior of groups of fireflies and with the pub- 

 lished statements regarding this peculiar action. It is 

 claimed in many independent reports that there exists at 

 times a certain unusual synchronism of flashing. Often 

 this synchronism is called rhythmical. Inthe course of 

 discussion synchronism of action has been described in 

 many different forms of animals, notably the swinging 

 movements of web-worms (16, 24), the rising and falling 

 of harvestmen (Phalangidae) (22, 30), the beating of the 

 wings of the pelican (30), the swaying of the bittern in 

 the grass (9), the wriggling of bees at the entrance of 



