SOMETIMES it seems that the lower down the ranks we are the harder we work, while our bosses laze about and reap the rewards. This is not just a human gripe, social insects exploit those lower down the pecking order, too. They have good reasons for this behaviour, though.
Jeremy Field and colleagues at University College London have found that the hairy-faced hover wasp, Liostenogaster flavolineata, has a hierarchical system in which the older wasps near the top work less than the lowly young wasps at the bottom.
This Malaysian species lives in groups of up to 10 females. The queen reproduces and the others gather food to feed her larvae. When the queen dies, the next-oldest female inherits the right to lay eggs.
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When Field鈥檚 team removed the second-in-line female, it had the effect of promoting the female that was third. As predicted she started to work less, as she was now closer in line to reproducing. Before promotion, she would have spent on average 62 per cent of her time foraging. After promotion, she foraged for only 27 per cent of the time (Nature, vol 441, p 214).
Foraging is a tiring and risky activity. 鈥淚f your future is brighter 鈥� you鈥檙e near the front of the queue 鈥� you should take fewer risks,鈥� says Field. 鈥淵ou should work less hard.鈥�
While it is well known that animals help their kin in order to propagate the 鈥渇amily鈥� genes, the future prospects of individual animals should also be taken into account to more fully understand social behaviour, such as aggression. 鈥淭he closer you are to the front of the queue, the more you have to gain from challenging those ahead of you,鈥� says Field.
