How insects behave 



drops of saliva and other fluids which the workers Hke, and for which 

 they continually lick and caress the larvae. The workers also obtain 

 honey-dew from aphids by caressing them with their antennae, and some 

 ants keep and tend colonies of aphids as if they were herds of cattle, for 

 the sake of their honey-dew. When it is considered that some of the 

 bigger ants also keep ants of a smaller species as slaves, and make them 

 do the heavy work of the nest, it seems that their societies have almost 

 reached the human level. 



Some ants can sting, but they are best known for their powerful bite. 

 Though the bite of one ant may be trivial to larger animals, the attack 

 of hundreds of ants at once can be most unpleasant, and may be danger- 

 ous. In the tropics the driver ants (Dorylinae) are nomadic, and move 

 about in dense columns, sometimes hundreds of yards long. As they 

 pass, they destroy all the insects and small mammals they meet, and 

 even the larger domestic animals may be killed if they are penned, and 

 cannot escape. 



Signs of Intelligence in Insects 



It is hard to say what is a sign of intelligence. Our own lives are con- 

 trolled by automatic, or reflex actions to a much greater extent than we 

 often imagine. Those of us who travel over the same route every day 

 come to make the whole journey in a mechanical fashion, not far 

 removed from the behaviour of an ant. Which of us has never been half- 

 way home before remembering that today he was to have done something 

 different like picking up a spool of thread or a loaf of breads or been 

 embarrassed to discover, in his wife's presence, a letter which should 

 have been mailed several days previously. 



A great many experiments have been made with the object of breaking 

 down the behaviour of insects into a chain of reflex actions. We have 

 mentioned the 'Hght-compass reaction' already. The basic experiment 

 is said to show that an ant which is walking steadily in a straight line 

 can be picked up and put down somewhere else, and will go forward in 

 a direction parallel to the first: therefore it was not going towards a 

 destination in a conscious way, but is. moving in a line that makes a 

 constant angle with the sun. If" the insect is covered up for a few hours 

 and then released it continues to make the same angle with the sun, even 

 though the sunUght now comes from a different direction. 



Experiments like this, though interesting in themselves, raise as many 

 problems as they solve. How does the insect get started on such a path; 

 what makes it choose that particular angle and what makes it eventually 

 decide to do something else ? Furthermore, how does it make the return 

 journey, and, as WiUiams asks, how do migrating insects maintain a 

 true direction in spite of the apparent movement of the sun ? 



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