The scourge of society: Parasites in Social Insects, by Paul Schmid-Hempel

Abstract

Princeton University Press, Monographs in Behavior and Ecology, 1999. £60.00 hbk, £24.95 pbk (xi + 409 pages)ISBN 0 691 05923 3 / 0 691 05924 1One of us studies parasites, and the other social insects. There is a large gulf between our two disciplines, a gulf that is bridged admirably by Paul Schmid-Hempel in an ambitious new book. Parasites in Social Insects synthesizes an eclectic and dispersed literature with such thoroughness and near-passion that, barring a global rush to study these parasites, it should stand for years to come as an authoritative reference. It has two great strengths.First of all, it is undeniably thorough. With 55 pages of references, a glossary, and a delightfully comprehensive appendix entitled simply ‘The Parasites of Social Insects', this is not a volume for the faint of heart. The first two chapters are devoted to introducing the main players – social insects and parasites. The following six chapters examine the interaction of these players from a variety of perspectives, from colony organization and parasitism to social evolution itself. Interspersed among these chapters are a host of tables, figures and boxes for detailed treatment of special topics. If there is anything you want to know about the parasites of social insects, this is the place to look.Second, Schmid-Hempel identifies a wealth of unplumbed research topics. He does so with such enthusiasm that there might well be a global rush to work on the parasites of social insects. Many of the lacunae he identifies mirror those in our understanding of host–parasite biology in general. Pure survey and/or demographic data are sorely lacking for many systems. We know little about the regulatory ability of parasites for host populations, little about the interplay of most host and parasite genetic systems, and little about the influence and extent of multiple infections.The very fact that the hosts in question are social allows for novel treatment of traditional questions in parasitology and sociobiology, to the benefit of both areas. Although we both found the book to be important, we disagreed on which sections we found most interesting and innovative. Parasitologists will be intrigued by the implications of social structure for interactions between hosts and parasites. For instance, the action of parasites on social insects can be viewed at two levels – that of the infected individual and that of the invaded colony. Transmission among colonies might favor aspects of parasite evolution that differ from those favored by transmission within colonies. Furthermore, para- site population dynamics are complicated by differential mortality rates of individuals versus colonies. Individual insects might show immunity to parasites, and entire colonies can display behavioral responses to cope with infections. Colony size itself is an important variable to include, and colony organization (division and labor and deployment of the worker force) can either enhance or retard transmission.Likewise, some concepts that are familiar to parasitologists might intrigue social insect biologists. For instance, island biogeographical theory has been applied to relationships between host ranges and parasite richness1xDritschilo, W. et al. Science. 1975; 190: 467–469Crossref | PubMedSee all References1; Schmid-Hempel notes that large colonies with large foraging potential might have a higher risk of encountering novel parasites. Many birds and mammals leave nests and foraging areas in the presence of parasites2xHausfater, G. and Sutherland, R. Nat. Hist. 1984; 93: 55–60See all References, 3xEmlen, J.T. Condor. 1986; 88: 110–111CrossrefSee all References; Schmid-Hempel suggests that parasites might motivate nest relocation in social insects.The book is not perfect. It is marred by a surprising number of typos and minor factual errors (e.g. incorrect descriptions of insect species and incorrect references to parasite biology), and we disagree with some conceptual treatments (e.g. the confounding of virulence and parasite reproduction). Such quibbles aside, Schmid-Hempel has produced an admirable book that is at once a remarkable work of scholarship and a source of inspiration for future study.