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 tiie time from deposi- 

 tion of the first egg until hatching of the first larva was assumed to be 

 the period of incubation, date of hatch mg 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 contaui very limited. For 

 the purpose of studymg 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, ^ 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 tune when placed where they can not receive sufficient moisture; but (and 

 this is the delicate point) this moisture must be maintained \vithrn 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. WTien, 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 cliief modification adopted was the use of a five-ceUed cage 

 instead of one of four cells, as described by Janet. Also, the ants 

 were not inclosed withm 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, smiulatmg 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 otlier 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.) 



