THE BEHAVIOUR OF INSECTS 121 



heat as they approach the light, and thus escape de- 

 struction. 



The behaviour of many insects is diametrically opposed 

 to that of night-flying moths. Most butterflies, for ex- 

 ample, attain the zenith of their activity in strong sun- 

 light, while their movements are arrested by the shadow 

 of a passing cloud. Again, the majority of insects shrink 

 from contact. This often proves a valuable trait, condu- 

 cive to safety ; but whether valuable or the reverse, the 

 response always occurs when the stimulus is forthcoming. 

 On the other hand, a few insects are known to be posi- 

 tively thigmotropic. They court touch. Their whole 

 being responds to the stimulus. Among them is a small 

 moth which is accustomed to squeeze itself into crevices 

 under loose bark or elsewhere. Now at first thought one 

 might suppose this to be a mere light-shunning reaction, 

 calculated to effect the creature's concealment. But the 

 German experimenter Loeb has proved otherwise. He 

 put some of the moths into a box one half of which was 

 covered with opaque material, the other half with glass. 

 On the floor of the box he arranged several sheets of glass, 

 raising them upon small blocks just enough to allow a 

 moth to squeeze its way beneath. As a result it was 

 found that the moths congregated beneath the sheets of 

 glass, even when exposed to full sunlight, in preference to 

 the dark corners of the box, which were easily accessible, 

 and where they would have been concealed from their 

 enemies. Clearly this moth's habit of hiding, though 

 apparently purposeful, is really a simple reaction to the 

 stimulus of pressure. It is useful only so long as the 

 creature's surroundings remain normal. 



But while simple responses to appropriate stimuli meet 

 the needs of plants and lowly animals, and have their 

 place even in the conduct of man himself — as when the 



