CO-ORDINATED RHYTHM IN INSECTS. 173 



CO-ORDINATED RHYTHM IN INSECTS; WITH A 



RECORD OF SOUND PRODUCTION IN 



AN APHID. 



By C. B. Williams, M.A., F.E.S. 



There are many scattered records of co-ordinated or collec- 

 tive action in insects scattered through entomological literature, 

 which, however, do not seem to have attracted the attention they 

 deserve. 



Mass migrations of locusts, butterflies and dragonflies are a 

 form of co-ordinated movement ; termites and processionary 

 ■caterpillars' have a " follow-my-leader " habit which is somewhat 

 related, and the up-and-down movement of clouds of midges, 

 other diptera and some may-flies also shows a collective spirit. 



Of greater interest are rhythmic actions which are carried 

 out by a number of insects simultaneously and synchronously. 

 Those so far recorded refer to the rhythmic production of light 

 and sound, and it is the purpose of the present note to draw 

 attention to the more interesting of these and to record a new 

 case of rhythmic sound production, which is of particular interest 

 in that it was found in an Aphid, in which family, so far as I 

 am aware, sound production has not yet been recorded. 



The existence of synchronised flashing of fire-flies has been 

 the subject of much dispute. My own observations during five 

 jears' residence in the West Indies and Tropical America, where 

 both Larnpyridae and Elateridse are abundant, have so far 

 produced no evidence for it, but in view of the circumstantial 

 accounts from other parts of the world its existence must 

 undoubtedly be admitted. 



Severin, as early as 1881 (' Nature,' vol. xxiv, p. 165) writing 

 of an unidentified Indian Lampyrid says : " The curious pulsation 

 or flashing of their light is remarkable, the insects on the tree 

 all act in perfect concert, i.e., five seconds of no light, then seven 

 rapid flashes; five seconds no light, seven flashes ; and so the 

 game continues throughout the dark hours." He states also 

 that insects on trees close together keep the same time, but 

 " groups of trees separated by one or two hundred yards may 

 not agree, and do not do so as a rule." 



Muir, speaking of fire-flies iu Borneo (' Hawaiian Ent. Bull.,' 

 vol. xiii, p. 67) says : " In some places thousands had congregated 

 together and all kept time with the pulsations of their light." 



A still more definite account is that given by Hess (' Biol. 

 Bull.,' vol. xxxviii, 1920, p. 39), when he describes Photinus con- 

 sanguineus flashing in concert in a small valley near Ithaca, N.Y. 

 He writes : " For a moment there was a blaze of flashing lights, 

 and then for a moment it was darkness, except for an occasional 

 flash which seemed to come from a different species." This was 

 noticed on two nights, on the second of which Hess found that 



