Insects and their world 



migration of insects (Williams, 1958). Although we know that a strong 

 wind may override the orientation of the migrating insects — i.e. the 

 direction in which they are facing and trying to move — this does not 

 explain the orientation but relegates it to a secondary importance. 



Insect Communities 

 It is not easy to draw a line between a swarm and a community, but one 

 might say that a swarm is essentially a temporary gathering for some 

 particular purpose (mating; hibernation), whereas a community is a 

 more lasting association. 



One of the best known of insect communities is one of aphids on 

 a garden plant. (Figs. 13, 20). Here can often be found all stages of one 

 or more generations living close together, feeding, reproducing, grow- 

 ing up. Such an assembly probably came about in a negative way, in 

 the sense that the insects concerned are peaceful plant-feeders, sur- 

 rounded by an abundance of food, and so there is no reason why they 

 should disperse. Those which thus spend their whole lives on a single 

 plant derive the biological advantage that they do not have to search 

 for the other sex, nor for a suitable place in which to lay eggs. 



Aphids are able, in a few weeks of summer, to build up very large 

 populations, using sedentary wingless females that reproduce partheno- 

 genetically, that is without the intervention of males. Winged females 



Fig. 61. A solitary bee, Order Hymenoptera-Aculeata 

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