32 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 4, NOS. 1-2. 



It should be noticed here that the females and males never 

 gave any test for acid, except in a single form (female of 

 Formica) ; also that as a rule only the species of genera which 

 are not provided with stings showed any considerable amount of 

 acid other than that which could be attributed to acid in the 

 alimentary tract or in the small acid sting gland. Cremastogaster 

 may prove to be an exception, but in this case most likely some 

 other acid is present. Forelius is a stingless ant and we should 

 expect to find it provided with acid, but it is neutral, probably 

 because of the substitution of a peculiar ethereal secretion to take 

 the place of the acid (see below). Pachycondyla, one of the 

 Ponerinse, although provided with a powerful sting, shows the 

 presence of a considerable amount of acid. The males of no 

 species secrete any acid, and as a general rule the females scarcely 

 ever more than a trace. 



THE distinctive; odors of somk species. 



No one who has ever collected ants extensively can have failed 

 to notice the very strong and distinctive odors possessed by many 

 species. Other species also, which are not particularly odorous, 

 yield peculiar scents when carefully examined. 



I. ECITON. 



All the species of this genus of ants which we have examined 

 (viz: E. ccecum, E. schmitti, E. sumicrasti, E. opacithorax, E. 

 calif ornicum, E. pilsoum) possess a strikingly similar and very 

 disagreeable odor. This odor, or one barely distinguishable from 

 it, is secreted in even a more marked degree by species of the 

 Neuropterous genus Chrysopa. In the latter insect it was long 

 ago described by Say ('59) as closely resembling human feces. 



The specimens of Eciton examined were subjected to distilla- 

 tion with steam and the first few cubic centimeters of the distil- 

 late collected. In this was found almost all the volatile odorous 

 substance. When isolated in this manner the fecal or indoloid 

 odor is even more pronounced than when the worker ants are 

 crushed between the fingers. As the odor strongly suggested 

 indol or some of its numerous disagreeably smelling derivatives, 

 tests were made for indol by crushing some of the ants on a piece 

 of plantinum foil with concentrated nitric acid, then evaporating 

 to a yellow residue which turned to a yellow-brown upon the addi- 

 tion of a small quantity of potassium hydroxide solution. The 



