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No. 81: May-Jun 1992

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Eusocial Beetles

The best-known eusocial animals are the ants, termites, and naked mole rats. As As biological observations accumulate, the phenomenon is being found elsewhere in the animal kingdom. The following quotation extends eusociality to the beetles and (in case you wondered) defines "eusociality":

"The weevil Austroplatypus incompertus lives in galleries in the heartwood of Eucalyptus trees. Colonies are initiated by solitary fertilized females and, when mature, manifest the three phenomena which characterize eusociality: overlapping generations, cooperative brood care and division into reproductive and sterile (unfertilized) castes. Each colony contains one fertilized and five or so unfertilized adult females, the job of the second group being to deal with predators and to extend and maintain the galleries."

(Anonymous; "Sociable Beetles," Nature, 356:111, 1992.)

Comment. Eusociality is somewhat of a puzzle in evolutionary theory because one must ask how the phenomenon arises, when it requires some individuals to forswear reproduction and thus give up the chance to pass their genes directly on to progeny. Explanations of such extreme altruism generally state that the nonbreeders are really helping to pass some (or even all) of their genes on by supporting the colony, for they are usually closely related to the breeding female.

From Science Frontiers #81, MAY-JUN 1992. 1992-2000 William R. Corliss