Harvestmen: The Biology of Opiliones

Ricardo Pinto-da-Rocha, Glauco Machado, & Gonazalo Giribet (Eds)

Harvard University Press, Cambridge, MA

2007; 597 pages

ISBN 13-978-0-674-02343-7

Price $125.00 (hard)

In a perfect world, there would be a definitive text for every taxonomic group of arthropods. And in that world, Pinto-da-Rocha et al.’s book would be on the shelf representing Opiliones. Easily lumped with spiders, harvestmen represent a diverse and often very abundant group of arthropods that are entirely unique in their physiology, morphology, and behavior. The Opiliones merit their own book, and entomologists need a better appreciation for this commonly encountered group.

Harvestmen is a wonderfully balanced and staggeringly complete treatment that covers the gauntlet of taxonomy and systematics, internal physiology, ecology, and behavior. It opens with a fascinating chapter on the history of harvestmen, especially from a human or cultural perspective, and from there skates through 15 chapters that touch on most aspects of the lives of Opiliones. One of my favorite chapters was the one on diet and foraging (Chapter 8), where the complexity of feeding ecology (they eat particles, not just fluids like most arachnids) and dietary breadth (they are appropriately referred to as omnivores, a fact often ignored by predator ecologists) of Opiliones is discussed at length. Another interesting chapter was on social behavior (Chapter 11), which discussed the levels of social organization that are known in harvestmen (primarily Goniosoma and Leiobunum spp.). All chapters are nested within the broader framework of the discipline, and discuss where harvestmen fit within the context of related organisms. This is taken to the extreme in the somewhat errant chapter on ecophysiology (Chapter 14), where only a trivial amount of detail focuses on Opiliones (most of the chapter discusses arachnids and insects). This is likely the case because so little work has been done on the ecophysiology (e.g., defined here as maintaining water and temperature equilibriums and biological rhythms) of harvestmen. The final chapter is a practical one that presents methods for various tasks that transcend work on the Opiliones. Methods for isolating DNA and creating molecular phylogenies, collecting, curating and measuring specimens, and preparing cells for viewing chromosomes present enough detail and references to get interested scientists headed in the right direction.

The chapter on taxonomy is a real gem, and bears special attention. At more than 150 pages (the book is 524 pages of text), this chapter presents dichotomous keys to the suborders, families, and subfamilies of the group (there are 45 extant families). For each group, the authors affirm their expertise by discussing the origins and histories of each family, the etymology of each name, morphological characterization (accompanied by images of pertinent features taken with a scanning electron microscope; approximately 40% of the pages have illustrations), distribution, and relationships with other groups. The taxonomy chapter is preceded by those on morphology and phylogenetics of the group, which helps prepare the reader for what is to come.

In addition to the breadth of material presented in Harvestmen, the depth of information was also impressive. On multiple occasions while reading, I had to shake my head in disbelief, silently remarking, “How did they find all of these records?” For example, Cockendolfer and Mitov (Chapter 9) were able to compile prey/host records of 100 pathogens and 300 predators of Opiliones from obscure sources, including a 1920 issue of the Ohio Journal of Science. Records like this are spotty in the literature, and summary tables that present much of what is known are a valuable basis for future exploration.

Both the chapter authors and the editors should be commended for their efforts. Twenty-five authors from across the globe contributed to the project, which gives the book an international relevance that is hard to achieve in single-authored texts. Each chapter is deftly authored by a leading expert, but rather than suffering from the disjointedness and redundancy that often plagues edited books, chapters complement one another to tell a complete story of the harvestmen. Clearly, the editors did not simply assign writing tasks and relax, but executed their jobs of communicating expectations and ensuring quality results. For this, Harvestmen: The Biology of Opiliones will remain a lasting contribution to biological literature.

The bottom line is that there simply isn’t very much information written about Opiliones, but what has been done is, with few exceptions, recorded and synthesized within broad context in Harvestmen. Entomologists, both graduate students and hardened veterans alike, would benefit strongly from having this text on their shelf. Oh, and to answer the question posed to every entomologist presenting spiders to school groups: No, harvestmen do not have the most toxic venom of insects, if only they had the ability to penetrate human skin. To the contrary, harvestmen have no venom glands at all.

Jonathan G. Lundgren

USDA-ARS

North Central Agricultural Research Laboratory Brookings, SD

E-mail: Jonathan.Lundgren@ars.usda.gov