Odour as a Basis for Orientated Movement in Ants

I. An historical sketch is given of the principal works on ant orientation. This suggests that ants can learn to orientate themselves by means of anything which affects their sense organs. The position of the nest is the conditioning stimulus, and the eventual purposive reaction to the thing is a conditioned reflex. 2. A description is given of some artificial ants' nests, how to make them and how to transfer ants to them expeditiously. 3. An apparatus is described, in which the movements of ants can be accurately followed and mapped with grease-paint. 4. It is shown that an unburdened Myrmica ruginodis worker travels a continuously looping course, while a burdened worker, on the other hand, or one violently stimulated, walks in straight lines with intermittent loops. 5. Experiments are given which demonstrate, that the continuously straight homeward course is formed from such straight lines, and that the loops are suppressed, and a good direction given, by isolated small spots of orientated odour. 6. It is shown that continuous odour trails are built up by the gradual accretion of these odour spots. 7. In a general conclusion, it is suggested that the cause of complication in ant behaviour is to be sought in redundancy of senses; the ant can perform the same action equally well by use of one sense, or of a number of senses.