BUCKINGHAM. — DIVISION OF LABOR AMONG ANTS. 443 



B. Work with Bartk Nests. ■ 



1. Environment i?i General. — It appeared that there are some ac- 

 tivities of ants which cannot be satisfactorily studied in natural nests, 

 and in order to watch the insects under more natural conditions than 

 were used for observations under division ^-1 (pp. 440-442), and to sub- 

 ject them, though in the laboratory, to an environment as nearly as 

 possible resembling that of their wild homes, Barth (:09) nests were 

 selected. Here the ants soon burrowed their chambers and galleries 

 in earth between two glass jars, a smaller set within a larger, the out- 

 side of which was always covered with thick black paper, except at 

 such times as the nests were examined. To prevent the escape of the 

 ants, screens of wire gauze were placed over the tops of the jars, which 

 Avere otherwise open, allowing free access of air. During the period 

 that these observations were made the nests were kept continuously 

 in a photographic dark room, with black walls, and a small window 

 through which daylight entered for some hours each day. In order to 

 produce the darkness normal to ants underground, this daylight was 

 closed out when the black paper was removed from the nests during 

 observation. The light needed in studying the movements of the ants 

 was secured by a 16-C. P. incandescent filament enclosed in a bulb of 

 ruby glass. This lamp served also another purpose, viz. to stimulate 

 the ants slightly, and thus make them more lively. 



2. Influences of Heat and Light. — That this stimulus was due to 

 beat and not to light was proved by the following experiment, tried on 

 two diiferent colonies of Camponotus herculeanas pictus. The results 

 of both were so nearly alike that I give only those of one. When the 

 temperature of the earth in the nest was 20° C, by a thermometer 

 previously placed there, and the ants were quiet, a water screen 2^ 

 inches thick was placed between the nest and the ruby bulb, which 

 •was about four inches distant from the nest. After five minutes the 

 ants were still perfectly quiet. The screen was then removed. Imme- 

 diately the ants began to move vigorously, and at the end of five min- 

 utes more the glass felt warmer to my hand where the light shone 

 on it than in other places. The temperature in the earth near the 

 ants had now gone up to 22° C, and the ants were carrying the larvae 

 toward the outer glass of the nest. The water screen was now replaced, 

 and the ants examined again at the end of another five minutes, when, 

 though the thermometer still registered 22° C, the ants were perfectly 

 quiet. After five minutes more with the screen still in place, the 

 room having become in general warmer, the thermometer in the earth 

 registered 22+° C, and the ants were perfectly quiet. Black paper 



