THE SOCIAL INSECTS 



particular about what they catch, and they will pick the blue 

 butterflies off their evening resting place on grass-stems, 

 besides other insects, or butcher's meat if they can get it. 

 Wasps need sweet stuffs and water. It is doubtful if they 

 often damage sound fruit, but they will enlarge any hole 

 started by other insects or by birds. Soft, over-ripe fruit is 

 readily attacked and wasps are very fond of blackberries in 

 the hedges. They visit flowers not only to catch flies but also 

 to get nectar, being very fond of figwort and wild parsnip. 

 Wasps have a sting with microscopic barbs, but these do 

 not prevent them from withdrawing it after use. They use 

 the sting only in defence, especially of the nest, not for killing 

 their prey — an interesting social trait distinguishing them 

 from the solitary species. One soon finds that a wasp at or 

 near its nest is a much fiercer enemy than one flying about 

 in the open. Association with the nest seems to call out a 

 characteristic aggressive behaviour pattern. Moreover, the 

 wasps from larger nests are fiercer, but this may be because 

 such nests are usually hotter inside and this increases all 

 aspects of insect activity. 



THE WASP SOCIETY 



Several entomologists have measured the temperatures of 

 wasp-colonies. According to Himmer, a thriving colony of 

 the common wasp runs at 26-36 C which is 5-1 5 C above 

 the temperature of its surroundings ; the temperature varies 

 much less than that of the air outside. The protected situation 

 of most nests, and the good insulation provided by the 

 envelopes, make some degree of temperature control easy, 

 since any heat produced will be lost only slowly. The 

 numerous larvae continually digesting rich food and the 

 crowds of active workers are of course at all times providing 

 the necessary central heating. 



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