112 ILLINOIS ACADEMY OP SCIENCE 



on essential points. The debate on some of these points 

 has already been begun in the literature, but no conclu- 

 sion agreeable to all has been drawn, 



(a) There is the widest divergence of opinion regard- 

 ing the regularity of the synchronism. If some of the 

 fireflies flashed in unison, how many in proportion were 

 'out of step 'I There was of course no check on the ap- 

 parent regularity of the synchronism. We know, es- 

 pecially from the work of MacDougall and Woodrow 

 that in rhythmical performance variations from strict 

 time can physically occur without a perceptible difference 

 in the maintenance of the rhythm. The quotations which 

 follow indicate positions assumed on this question by the 

 observers. 



''There must have been several thousand insects in 

 each tree, yet the synchronism was so perfect that rarely 

 or never did a single firefly flash at the wrong time." (25) 



"From time to time, as if moved by a common impulse, 

 great numbers would flash so closely in unison over the 

 entire field that an extensive sheet of tiny light-points 

 would gleam upon the vision for a moment — and then 

 vanish." (1) 



"The majority of the fireflies were flashing in unison 

 but there were some which did not time their flashes with 

 the majority." (4) 



"The flashes were not perhaps as regular as an army 

 officer would like to see in regimental drills but were so 

 rhythmic that any one would take note of their action." 

 (20) 



"I frequently noticed that small trees and shrubs 

 would be more aglow at certain times than at others, but 

 I never happened to observe a time when a small tree or 

 shrub was all alight one instant and dark the next. In 

 my experience there were always some fireflies flashing 

 in the 'dark' periods. The times of greatest light oc- 

 curred when the greatest number of varying flashes co- 

 incided." (10) 



" * * * It was soon evident that while at a given 

 instant one tree may have been more highly illuminated 



