1881]. NATURAL SCIENCES OF PHILADELPHIA. 61 



species (so far as known), and why so limited a number of workers 

 in the formicaries of these two species should develop the round 

 abdomen, are questions that provoke sufficient wonder, but j-ield 

 scant satisfaction. 



XI. Possible Organs of Stridl'lation in Ants. 



The segmental plates of the abdomen are composed of numer- 

 ous hexagonal epithelial scales, PI. YII, fig. 48, which present a 

 very beautiful appearance, as of delicate mosaics, when viewed 

 througli a microscope. When a profile view of one of these plates 

 is exposed to the lens, as at fig. 49, the scales are seen to be 

 imbricated, that is, to overlap each other like tiles on a house 

 roof, and show the serrate edge figured in the cuts, figs. 49 and 

 50. The former (49) is drawn from a section of Gamponotus 

 inflatus, and the latter (50) from Hortus-deorum. This serrate 

 edge not only shows upon the external part of the plate e. ab. pL, 

 but upon the imbricated portion, i. ab. pi. By referring to the 

 manner in which the one part overlaps the other shown at figs. 

 53, 54, it may be seen that a backward and forward motion of 

 the plates iipon each other might produce a faint rasping sound. 

 That this motion is entirely possible can hardly be doubted. The 

 abdominal plates are continually, though gradually, sliding out 

 and in, like the parts of a telescope, under the expansion and 

 contraction of the crop, as the ant feeds or regurgitates the con- 

 tained nectar. All that is required to have the complete condi- 

 tions for stridulation seems, therefore, to be the muscular ability 

 to perform this action rapidly; which, it appears to me, ants cer- 

 tainly possess. 



I have often noticed the peculiar hiss-z-z-z ! which arises from 

 an excited colonj^ or column of ants, a sound which grows in 

 intensity according to the degree of excitement. I have also met 

 an opinion prevalent among ordinary observers, that the ants 

 produce this sound by some organ analogous to some one of those 

 by which other insects produce musical notes or noises — in short 

 (to use the popular phrase), that "ants sing." But I have here- 

 tofore been disposed to consider the noise referred to simply as 

 the result of friction of a great multitude of insects moving rapidly 

 over the surface of the earth, the litter of leaves, twigs, etc., and 

 against the hard, shell-like bodies of their fellows, or possibly (also) 

 b}' the gratings of the hard tooth-like mandibles upon each other. 



