446 PROCEEDINGS OF THE AMERICAN ACADEMY. 



SO that it can be carried into the nest, or so that it is suitable for 

 eating. " Regurgitating food " is a fairly common habit among ants ; 

 when they have been feeding, they sometimes disgorge some of the 

 food to their companions. The process of " licking " is minutely de- 

 scribed by McCook ('79, p. 125) for Pogonomyrmex barbatus as clean- 

 ing each other. The ant which is doing the licking or cleaning passes 

 all over the body of the other ant with her mouth parts, which are 

 constantly in active motion. The ant which is being licked stands 

 still, apparently content to have the process carried on. Wheeler 

 (: 03", pp. 43-44) says in regard to licking in Leptothorax that there 

 can be little doubt that the ants obtain some substance from the body 

 of the Myrmicas, but it is difficult to ascertain its nature. He thinks 

 it may be a secretion of the cutaneous glands, or merely the salivary 

 secretion that has been spread over the Myrmicas by the mutual 

 licking in which they indulge. Later he (Wheeler : 07=, p. 70) speaks 

 of it as an " oleaginous secretion." By " responding to disturbances of 

 the nest " I mean such disturbances, for example, as knocking on logs 

 in which Camponotus pictus for the most part lives, jarring the artifi- 

 cial nests, or tearing open log nests or earth nests. " Guarding " sig- 

 nifies such habits for the protection of the nest as are found in 

 Colobopsis (see p. 428). Although these guards allow all the in- 

 habitants of the nest free passage, they nevertheless keep out all 

 intruders. 



V. Studies of Camponotus. 

 A. Camponotus americanus. 



In the observations on the various activities of Camponotus ameri- 

 canus I have tried to discover (1) the proportion of the whole number 

 of worker ants which engaged in a given activity, (2) the extent to 

 which each individual was engaged in that activity, and (3) the rela- 

 tion, if any, between the size of the individuals and the nature of their 

 activities. 



1. Foraging. 



1. Methods. — In order to determine to what extent this species is 

 attracted by food near at hand, and which individuals respond to this 

 stimulus, any arrangement which would allow one to know definitely 

 which individuals, if any, had had recourse to the food (or at least to 

 the chamber containing it) during a fixed interval of time w^ould afford 

 a basis for judging of the general effect of food as a stimulus and for 

 determining the ])articular ants or classes of ants stimulated by it. 

 The method adopted to attain these ends w^as as follows : The ants 



