Signalers and Receivers: Mechanisms and Evolution of Arthropod Communication
- Michael D. Greenfield
Communication between members of one's own kind is one of the most important behavioural acts that any animal must perform well if its genes are to be represented in the next generation. An alpha male (of any ilk) who has gained his 'top dog' advantage by virtue of his competitive prowess has fought for nought if his actions don't translate eventually into puppies of similar ilk.
This little book is ostensibly about how arthropods, but mainly insects, produce and consume signals in the behavioural commerce of competition and courtship. The evolutionary issues at stake, following Darwin, are neatly divided into the primary sensory modalities of sound, smell, sight and touch, and could as well be applied to fish, frogs, birds or mammals (and, if we follow the evolutionary psychologists, humans).
The book's subtitle pays homage to the fact that the diverse and numerous arthropods — most prominently, insects and spiders by land, and crabs and lobsters by sea — have some of the most varied modes of communication in the animal kingdom. Every possible sensory modality known (and some particular only to them) is exploited by arthropods for transmitting and receiving communication and signals. As a consequence, the topic of arthropod communication has generated a huge literature, and the book lists 71 pages of references, making it a valuable resource for this alone. The text itself is just 295 pages, but Michael Greenfield has done a thoughtful, excellent job of highlighting the central theoretical issues and selecting salient examples from this huge literature.
The chemical senses, smell and taste, are extremely important in arthropods and, depending on the species, mediate everything from finding food to finding a mate. Through hormonal actions they also mediate developmental decisions. The chemical senses seem to be crucial links in the behavioural networks that enable the evolution of hierarchically complex societies of individuals. Greenfield discusses the behavioural and evolutionary aspects of olfaction admirably, primarily within the context of sexual advertisement and courtship, especially in moths, where much of the work has been done.
But in his coverage of moths, I wish that he had delved more deeply into the mechanistic aspects of communication, particularly its physiology and biochemistry, where so much excellent work has been done over the past 30 years. Thanks to work in selected model systems, such as the tobacco hornworm moth (Manduca sexta), we know a lot about molecular receptor systems, especially the neural systems that underlie developmental systems and courtship behaviour, which make up the neuroethology of communication. On the other hand, the virtues of this book are its conciseness and clear writing, so I suppose the author had to be selective about what to include.
The lion's share of attention is given to the chapter on mechanical signals, sound and vibration, which are the focus of the author's own research. From a comparative point of view, acoustic signalling is the province of only two groups of animals, the arthropods and the chordates. Greenfield devotes much of his narrative to the remarkably diverse ways and means by which insects produce and receive acoustic signals. Insects produce signals by rubbing body parts together (stridulation), substrate vibration, tymbal mechanisms (in cicadas) and hissing; all are described, primarily in narrative form.
Here there appears to be a lost opportunity in the author's book plan. Although the book contains some excellent diagrams and other pictorial material, it could have done with at least twice as many depictions of mechanisms and even pictures of the animals themselves. Most of the illustrations are drawings, which is fortunate because the photographs are poorly reproduced. I was also surprised to see how little the author devotes to acoustic communication in the fruitfly Drosophila, given the status of D. melanogaster as a model organism, especially for behavioural-genetics studies.
The chapter on vision is the shortest but provides a sketchy outline on central issues of visual communication. Perhaps Greenfield was aware that the subject of arthropod vision has been masterfully covered in a recent book on the subject by Michael Land, Animal Eyes (Oxford University Press, 2001).
Signalers and Receivers concludes with a chapter on sexual selection and the evolution of signals, which is appropriate because insects have always been a rich source of insight into these topics. It is perhaps no accident that some of the major modern thinkers in evolutionary behaviour theory were themselves entomologists, including W. D. Hamilton, R. D. Alexander and E. O. Wilson — so too was Alfred Kinsey, but that's another story. However, the five pages devoted to this chapter are so sketchy that I was left disappointed because insect studies have so much to bring to the general discussion. However, evolutionary issues arise and are discussed throughout the book.
In summary, this is a valuable addition to the literature on animal communication at an introductory level. Greenfield's book is worthwhile precisely because it is brief. I will recommend this book for undergraduate courses and for the generalist reader who wants to know more about this interesting subject. Advanced readers would also enjoy reading the book but may find it wanting for depth and detail, although they will greatly appreciate the reference list.