THE SOCIAL INSECTS 



which a number hatched from one egg-group hide together 

 by day and from which they come out to feed by night. Any 

 advantage acquired by such association is essentially a social 

 one, but their behaviour has never become very elaborate. 

 A caterpillar is a relatively simple insect compared with, 

 say, an ant, and is in any case only a transitory stage. 



All the advanced insect societies appear to have arisen 

 from a progressive development of maternal care, the social 

 unit being the mother and her offspring rather than a col- 

 lection of brothers and sisters. The first essential step is that 

 the female should continue to have contact with her eggs 

 after she has laid them, and usually after they have hatched. 

 It is impossible even to list the immense variety of ways in 

 which insects have improved on the simple act of laying their 

 eggs on or near the larval food-supply. Some ichneumon 

 wasps, instead of laying their eggs straight into the body of a 

 caterpillar, carry them about hanging from the ovipositor 

 until they hatch. Only then do they put the young grubs on 

 to the sawfly larva which forms their food. Though this 

 particular type of behaviour seems to have been a blind alley, 

 anything which prolongs the contact between the mother 

 and her young is a start on a possible road to social life. A 

 number of plant-feeding or sometimes predatory bugs brood 

 over their eggs and younger nymphs. The nymphs tend 

 to form a compact group and the female stands over them 

 when anything approaches, rather like a hen brooding over 

 her chickens. This example is also comparable with the 

 cinnabar caterpillars already mentioned, since the bugs are 

 brightly coloured and have an evil smell. 



A group of insects, known as the Embiids, which are 

 found in most of the warmer parts of the world, are often 

 cited as an example of rudimentary social behaviour. They 

 are also of interest because they seem to be allied to the 



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