THE TERMITES 



culture such as the accumulation of the water given out 

 during respiration. The effect of crowding on the rate of 

 egg-laying is, however, likely to be due to nervous stimu- 

 lation. 



A closer analogy to what is presumed to happen in termites 

 is found in the migratory locust. In this insect, both in 

 nature and in laboratory cultures, the individual reared in a 

 crowd is profoundly different from one reared in isolation. 

 It takes on a different colour, the shape of the thorax becomes 

 perceptibly different, the wings become longer and the 

 behaviour is entirely altered. The nymphs tend to march 

 about together in bands instead of hopping about as indi- 

 viduals, and the adults tend to undertake migrations in large 

 swarms. It is certain that these differences are mainly due 

 to crowding, and probable that they arise mainly from the 

 sensory impressions received through the eyes. Living 

 together in a crowd and seeing their fellows moving, makes 

 each individual more active, and this in turn in some way 

 alters the colour and shape during development. No doubt 

 this is a much simpler process than those which would have 

 to be invoked in the case of termites, since in the latter several 

 different developmental paths are open and each path is 

 chosen in approximately the right proportions. The theory 

 of the group effect in termites cannot at the moment be 

 regarded as more than an interesting hypothesis requiring 

 further work. 



GROWTH AND DIVISION OF COLONIES 



The multiplication of termite colonies by the marriage 

 flight of the winged adults, though the normal method, is 

 not the only one. In some species, e.g. Calotermes, if the 

 nest becomes very diffuse and spreads a long distance under- 

 ground, the inhibition exercised by the royal couple may be 



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