Insects and their world 



Fig. 59. An ichneumon-fly, Order Hymenoptera-Parasitica 



into the nest, where it grows up. Thorpe points out that: 'It seems likely 

 that the fly can distinguish visually between: (i) workers and soldiers; 

 (2) "empty-handed workers" and laden ones; and possibly (3) workers 

 travelling away from the nest and workers travelling nestwards.' 



Instincts of this kind are inborn and inherited, and exist somewhere 

 in the nervous system of the insect, all ready to be triggered off by some 

 outside stimulus. If no opportunity occurs for the mechanism to go off" 

 normally it becomes 'trigger-happy' (or, more formally, 'the threshold 

 of release is lowered '), and the insect may go through the motions at 

 quite the wrong time. In this, after all, it is only like a small child at a 

 school concert, who laboriously learns a part, and then, impatient of 

 waiting, goes through his act from the wrong cue. 



Instinctive behaviour in insects can be modified by training, showing 

 that insects are not at the mercy of entirely automatic, mechanic^ 

 behaviour. A single example is the way in which bee-keepers persuade 

 a colony of bees to move from one hive to another, or even combine two 

 colonies in one hive. To avoid strife among the bees, the move is made 

 by a succession of small changes, allowing time for the bees to become 

 accustomed to each one before making the next move. 



