INTEGRATION OF AGGREGATIONS 91 



the observer is the fact that this synchronism is confined to locaHties 



bordering on streams, or to low, water-saturated ground 



Around Bangkok it is commonly known that the synchronal flashing 

 of fireflies is confined to one particular tree, the 'ton lampoo' of the 

 Siamese — Sonneratia acida. In all of the observations which the writ- 

 er has made, no exceptions to this have been found, but whether this 

 particular tree is the gathering-place of the insects in cases of syn- 

 chronism reported from other parts of the East is a question. 



''The fact that Sonneratia acida is the tree on which the insects 

 congregate around Bangkok leads one to question the statement that 

 has been frequently made to the effect that the synchronal flashing 

 of the fireflies is a mating adaptation. S. acida is found both in man- 

 grove associations, and also as a solitary tree growing along the 

 banks of streams. In these latter cases the roots of the tree are often 

 immersed in water, the tree at times standing several feet from the 

 bank. If the females of the species are wingless, as is the case with 

 the majority of the North American Lampyridae, there would be no 

 opportunity for them to approach the tree. Furthermore, at no time 

 have females been found on a tree of actively synchronizing insects, 

 or within its vicinity. Observations on this point have been repeated- 

 ly made and have been corroborated by local entomologists who 

 have become interested in the problem. 



"Perhaps one of the most popular theories as to the cause of 

 synchronism is that of 'sympathy.' According to this idea there is 

 some particular insect which acts as a pace-maker for the rest, and 

 they follow him, regulating their flashes by his. However, due to the 

 fact that the insects are scattered quite generally over a tree and are 

 not within sight of any one particular animal, this appears to be 

 quite impossible. Furthermore, any follow-the-leader action on the 

 part of the insects would result in a wave of light passing over the 

 tree and originating from a definite point, a fact which is not the 

 case once the synchronism has begun. 



"It is possible to inhibit the synchronism of a tree of insects by ex- 

 posing them to a bright light for about a minute. When the fight is 

 turned off, the synchronism returns having its origin, apparently, in 

 some individual or group generally located in the central part of the 



