86 Instinct and Intelligence 



friendly terms. Having no antennae, and there- 

 fore no sense of smell, they can no longer dis- 

 tinguish friend from foe. Male insects after 

 their antennas have been removed do not recog- 

 nise the female; they will pass close to their 

 favourite food without noticing it; they guide 

 themselves by the sense of smell, and when 

 their antennae are removed fail to retrace 

 their way home from a distance or to recognise 

 their companions when they reach their 

 nests. 1 



If an ant is smeared with matter pressed from 

 the bodies of its nest companions, and then put 

 back among the latter, they take no notice of 

 the stained insect. But if an ant is smeared with 

 fluid pressed from the bodies of a hostile nest, 

 and then returned among its companions they 

 at once attack and kill it. Evidently it is the 

 odour of the fluids in the two cases which affects 

 the actions of the ants through impressions made 

 on their olfactory sensory organs, impressions 

 which pass through the antennary nerves to the 

 olfactory lobes of the insect's brain and re- 



1 The Senses of Insects, by A. Forel, translated into English 

 by Macleod Yearsley, F.R.C.S., pp. 69, 129. 



