stridulation in ants. 201 
ants, who are all in violent movement at once. The 
passage from Lubbock, quoted above, however, leads me 
to think that this is not so, but that the audible noise is 
the sum of the individual stridulations of countless ants. 
The tail-wagging of Cremastogaster would account for the 
sound made by them being louder, though they are so 
much smaller than Camponotus or Polyrhacis.* I had 
asked Mi. Aitken to make some experiments to check 
the results | thought I had obtained. Members will no 
doubt recognise his hand in the following characteristic 
note, which fully supports my contention :—‘I do not 
need to experiment. ‘The roar raised by a squadron of 
Lobopelta, if you poke at them with a straw, does not 
require to be listened for with your hand to your ear. I 
should like, however, to know something about the 
organs by which it is produced. Military drums, I 
should think.’”’ 
The evidence of two such good naturalists as Messrs. 
Wroughton and Aitken is very valuable, and Iam glad 
to be able to bring forward a more direct and conclusive 
demonstration, by describing and figuring the organs, 
and by saying that I have been able to make them work 
so as to produce audible results. By operating with the 
stridulating organs of several species of Atta, a quite 
audible sound is produced. A very distinct sound is 
also heard when the appropriate movements are made 
with Dinoponera grandis and Paltothyreus commutatus, 
and I have also been able to hear an extremely faint 
sound by working with the abdomen of a species of 
Pscudomyrma. 
I will now give descriptions of the stridulating organs 
in several species of ants selected from various divisions 
of the family, and will conclude with a summary dealing 
with some of the points of particular interest. 
The stridulating organ consists of a series of delicate 
lines placed on the middle of the base of the dorsum in 
the 38rd abdominal segment, and in addition to this of a 
special development of the posterior edge of the previous 
segment. Between these two parts there is a co-adapta- 
tion. 
* Camponotus and Polyrhacis do not stridulate ; they belong to 
the subfamily Camponotides, in which group there are no stridu- 
lating organs.—D. S. 
TRANS, ENT, SOC, LOND. 1898.—parRtT Il. (JUNE,) P 
