METHODS OF STUDY. 37 
stages. In some of the records given below single individuals have 
been kept under observation from deposition of the egg, through larval 
and pupal stages, to the adult. In other cases the time from deposi- 
tion of the first egg until hatching of the first larva was assumed to be 
the period of incubation, date of hatching of first larva to formation 
of first pupa the duration of the larval period, etc. 
While these cages were invaluable in studying the life history of the 
ants, the small amount of space available for them between the glass 
plates made the number of ants they would contain very limited. For 
the purpose of studying the general habits of large colonies of ants a 
modification of the Janet cage was used. As its name implies, this cage 
was invented by Mr. Charles Janet, 1 and is described by him as follows: 
The apparatus (an artificial horizontal nest of porous mineral substance) described 
in this treatise gives, in reference to the raising of ants, remarkable results. Ants die 
in a short time when placed where they can not receive sufficient moisture ; but (and 
this is the delicate point) this moisture must be maintained within certain limits. 
The apparatus invented up to the present do not solve this difficulty. Furthermore, 
they do not lend themselves easily to observation, nor do they permit one to withdraw 
with ease specimens when needed. The artificial nest is formed of a block of plaster, 
or any other porous substance, which has hollowed out of it a certain number of small 
cells, placed one after the other and communicating. These cells are covered with an 
opaque slab designed to keep the cells dark between the periods of observation. A cup 
of water placed at the end of the block allows it to absorb moisture. The cell nearest 
this cup is the dampest, and the one farthest away the driest. I leave this last always 
light so that it resembles, for the breeding under observation, a space outside of the 
nest. If the water-cell has been kept too moist, the ants go into the cell farthest away, 
that is to say the driest. When, on the contrary, the apparatus becomes too dry the 
ants return to the walls of the cell containing the water, which is always damper than 
the other parts of the nest. They can thus choose for themselves the part of the nest 
presenting the degree of moisture which suits them best. 
The chief modification adopted was the use of a five-celled cage 
instead of one of four cells, as described by Janet. Also, the ants 
were not inclosed within the cage, but were allowed to enter or leave 
at will. To permit of this the Janet cages were placed upon plat- 
forms, which stood in running water. These platforms were consid- 
erably larger than the cages, and this gave the workers quite an area 
to forage over, simulating natural conditions quite closely. The food 
was placed upon the platform, outside the nest, and the workers thus 
had to carry it in and feed the larvae in the same manner in which it 
was done outdoors. These cages had sufficient capacity for many 
thousands of ants. They were used for observing the behavior of 
large colonies and for the purpose of noting the effects of poisons 
and various control measures. 
1 Studies on ants. Note 2. Apparatus for the raising and observation of ants and other small animals 
which require a moist atmosphere. Extract Ann. Ent. Soc. France, Mar. 10, 1893; vol. 62, pp. 467-482, 
figs. 11-12. (Translated by Miss A. O'Conor.) 
