The Other Insect Societies

  • James T. Costa
Belknap Press: 2006. 812 pp. $59.95, £38.95 0674021630 | ISBN: 0-674-02163-0

For much of its history, the study of insect sociality has been dominated by the study of ants, bees and wasps (the order Hymenoptera) and driven by a single paradigm (genetic relatedness and kin selection). The other social arthropods have been largely ignored or relegated to fringe status. James T. Costa seeks to correct this oversight with his book The Other Insect Societies. He succeeds in showcasing the true diversity of social behaviour among insects, spiders and crustaceans, and provides support for a set of alternative hypotheses about social evolution that should stimulate research and fuel scientific debate for years to come.

Perhaps it is not surprising that bees, ants and wasps have historically taken the limelight at the expense of the 'other insect societies'. They are nearly ubiquitous and economically important, and have fascinating social organization and seemingly inexplicable altruistic tendencies. As a result, these hymenopterans provide a well-researched database on which to develop an overarching framework of evolutionary theory. W. D. Hamilton's theory of kin selection (J. Theor. Biol. 7, 1–16, 17–52; 1964) explains the role of genetic relatedness in the evolution of altruistic behaviour, such as reproductive division of labour, with sterile members effectively caring for the reproductive members. This has become a pivotal concept in arthropod sociobiology, popularized in E. O. Wilson's book The Insect Societies (Belknap, 1971). However, as Costa's impressive compilation makes clear, there are likely to be many evolutionary pathways to sociality that may or may not involve kin selection.

Let's stick together: weevil larvae (of the order Coleoptera) aggregate on a leaf. Credit: J. T. COSTA

Looking beyond kin selection and relatedness, Costa emphasizes the need to disentangle the concepts of eusociality and sociality, and to abandon the widely embraced 'terminological hierarchies' of sociobiology (subsocial, communal, quasisocial, semisocial, eusocial). The path delineated by this terminology is ultimately framed around the key criteria that define eusociality: overlapping generations, reproductive division of labour, and sterile worker castes. Set forth most prominently by Wilson in Sociobiology (Belknap, 1975), these criteria for eusociality have been the gold standard by which all non-eusocial arthropod societies have been measured and compared. Costa effectively argues that this terminology has so constrained our perspective that the role of ecological factors in the evolution of arthropod sociality has been largely unrecognized. That is not to say that the classic criteria of eusociality are without value; however, when used as a framework to examine non-eusocial insect societies, they are often as restrictive as they are enlightening.

Ultimately, Costa synthesizes ideas from his own work with those of others to create new categorizations and terminologies with broader applicability. Constructing his review of insect societies around four primary categories — maternal and biparental care, paternal care, 'fortress defenders' and 'larval societies' — he applies a framework that concentrates as much on the ecological context of sociality as the type of social structure.

The book provides a careful treatment of both the well-studied and the relatively obscure taxa that make up the non-eusocial social insects. Several chapters are focused on selected representatives of the Coleoptera (for example, bark and ambrosia beetles, weevils, fungus beetles, whirligig and burying beetles), Lepidoptera (social caterpillars, webworms, swallowtails and silk moths) and Hemiptera (aphids, treehoppers, cicadas and leafhoppers) and are organized by ecological similarities. Costa also delves into obscure resources to provide fascinating accounts of the lesser-known taxa with relatively scarce ecological and behavioural data, such as web-spinners (Embiidina), sawflies (Symphyta), earwigs (Dermaptera) and thrips (Thysanoptera). He also includes non-insect arthropods, such as arachnids, millipedes, centipedes and crustaceans.

Although others have attempted to synthesize the literature on non-eusocial insect societies, this is the first major single-author monograph on the topic for more than a decade. We found little to criticize, even in such a large book. Perhaps graphical representations of data might have improved the strength of certain scientific arguments, in place of some of the line drawings, which seem oddly placed and in many cases have no clear connection to the text. On the plus side, many of the taxa covered in the book are illustrated with stunning colour photographs.

Costa takes a refreshingly unbiased approach to examining these fascinating societies, providing insight into how non-eusocial insect societies are structured, as well as details of their systematics, natural history, ecology and anatomy. His writing is scholarly enough to appeal to professionals, yet it is accessible enough to enlighten any interested reader. His book gives the 'other insect societies' well-deserved time in the spotlight, and will be a valuable and appealing addition to the libraries of academics and readers of scientific natural history alike.