Heming, Bruce S. ed.: Insect Development and Evolution. Comstock Publishing Associates, a division of Cornell University Press, Ithaca and London, 2003. xv + 444 pp. Hardcover US $85. ISBN 0-8014-3933-7.
Basically, developmental biologists and evolutionary biologists are two very different brands of scientists. The questions they ask, the methods they use, the kind of explanation they eventually aim to get are hardly the same. Everything is different, from the broadest epistemological paradigms within which they operate to the everyday language in which their studies are eventually reported. To a certain extent, however, the deep chasm between their research fields is matter of tradition more than matter of necessity. Increasingly focussed efforts are indeed been provided towards an intertwining of these two research traditions, in the form of an integrated evolutionary developmental biology, or evo-devo. Up to date, developmental biologists have contributed more than evolutionary biologists to giving content and shape to this new discipline and this still one-sided effort is clearly visible in the field's growing literature. Heming's otherwise excellent book is no exception.
Insect Development and Evolution is basically a book on insect development. A uniquely comprehensive, well researched and well written one, where descriptive information and experimental evidence are given the share of space either of them deserves. Whenever adequate, exhaustive historical detail is provided. For example, Heming offers an articulated account of classical work on determinants, physiological centres, gradients and fate maps, as an introduction to a very good chapter on the molecular genetics of pattern formation in the embryo of Drosophila melanogaster. In later chapters he summarises a series of historical experiments on the action of hormones in inducing moulting and metamorphosis and provides a detailed overview of old and new theories about the relationship between the postembryonic developmental schedules of heterometabolous and holometabolous insects.
But what about evolution? The whole final chapter (‘Ontogeny and Hexapod Evolution’) is devoted to this subject but, a bit surprisingly, a great many pages here are spent summarizing basic concepts in evolutionary biology (e.g. natural selection, speciation, adaptive radiation, heterochrony and Haeckel's biogenetic law), or outlining the fossil record of the individual insect orders. All this stuff has clearly to do with evolution, but not, perhaps, of the sort one would expect to find in a book basically devoted to developmental biology.
In three ways, however, Heming moves towards an evo-devo approach. First, by repeatedly using a ‘consensus phylogeny’ of insect orders onto which information is plotted as to number and type of ovarioles, copulatory position, mechanism of sperm transfer, oviposition type, viviparity, blastokinesis, larval and pupal type, and type of postembryonic development. The schemes, however, are not accompanied but a true phylogenetic analysis. Secondly, Heming often discusses the adaptive significance of morphological, behavioural or physiological traits. Thirdly, and more important, he takes advantages of the wonderful progress in Drosophila developmental genetics for exploring possible key events in the evolution of the insect body plan. This valuable effort brings him closer to an integrated evo-devo approach, but this is also where one perceives the shortcomings of the current approach centred on the study of very few model organisms. There is much more to insects than D. melanogaster, even among those, the holometabolans, which share with the fruitfly the mechanisms, and the consequences, of a dramatic metamorphosis. To get an appreciation of what we should know of insects beetles, butterflies, on neuropterans, it would be enough to consider that their imaginal discs have probably a more limited role in shaping the adult body than have those of Drosophila. A comparative overview of insect imaginal discs, however, is something one would look for in vain in Heming’ book, or in the recent (and also most interesting) Imaginal Discs by L. I. Held Jr (2002).
At any rate, while waiting (or working) for a full-fledged evo-devo approach to the study of insects, we shall wholeheartedly congratulate Bruce Heming for this excellent book, by far the best comprehensive survey of insect developmental biology available to date.
