THE INSECT WORLD 



correct path is learnt. A good deal of insect behaviour could 

 be of this type; but unless conditions are controlled so that 

 it is known what stimuli are being received, it is impossible 

 to be sure that the insect is not making a series of instan- 

 taneous reactions. It might, for instance, reach a source of 

 food whose smell became stronger and stronger the more 

 nearly it was approached, without any need to learn the 

 way. 



FINDING THE WAY 



A more complex type of behaviour is described as insight 

 learning. What this means can be explained by an example, 

 though there is still some dispute whether any insect is cap- 

 able of it. (In my own view, it is no longer possible to deny 

 some power of insight learning to some of the Hymen- 

 optera, including not only social forms like ants, but also the 

 solitary, nest-building bees and wasps). All bees and wasps 

 make a careful study of the nest-site, walking or flying round 

 it in a number of widening spirals or circles. It is often 

 possible to prove that they are memorising small local land- 

 marks. 



Thus, Tinbergen describes how a circle of pine-cones was 

 made round the burrow of the wasp, Philanthus, when the 

 wasp was inside. When she came out, she flew round 

 studying the site for six seconds. While the wasp was away 

 hunting the cones were moved to form a circle one foot 

 away from the nest. When the wasp returned after ninety 

 minutes with a captured honeybee, she looked for the nest 

 in the circle of pine-cones and in no case found the entrance 

 until the cones were again placed round it. Experiments with 

 ants, to be described later, show that both the position of the 

 sun in the sky, and also a scent-trail, may help to indicate a 

 path. 



29 



