Pheromone Communication in Moths: Evolution, Behavior, and Application

Moths are everywhere and seem so familiar: adults fly to our outside lights in the dark, pupae we find in our stored grain, caterpillars hang from trees in front of us on our hike or chew on our favorite vegetable in the garden. We may collect the large and colorful species (Luna moth or Atlas moth, for example) or we may even keep a colony or two in our lab to study them. But how do they “talk” to each other and avoid miscommunication (attempting to mate with the wrong species)? Moths constitute the majority of the species within Lepidoptera, which is, as Löfstedt et al. note in Chapter 4, “the insect order for which we have the most extensive knowledge of volatile sex pheromones and the roles and mechanisms of pheromonal communication.” This new book looks at moth communication from many different angles—evolutionary biology, chemistry, biochemistry, behavioral biology, and pest management—true to the interdisciplinary nature of the subject. Should the reader decide to become familiar with the history and basic concepts, I recommend focusing on Part One, which provides a comprehensive introduction, setting the stage for the rest of the book. Naturally for a book with chapters authored by different scientists from different fields, the degree of detail varies from chapter to chapter. Chemistry and biosynthesis enthusiasts with a knack for phylogeny and evolutionary thinking will especially like Chapter 4, “Evolutionary Patterns of Pheromone Diversity in Lepidoptera,” and those keen on neurophysiology will enjoy reading Chapter 10, “Moth Sex Pheromone Olfaction: Flux and Flexibility in the Coordinated Confluences of Visual and Olfactory Pathways.” It is very helpful that terminology and compound coding are well standardized across chapters (with any deviations indicated), and the book contains excellent figures and tables for clarity. Part Two showcases studies focused on individual species (such as Ostrinia nubilalis in Chapter 15 or Utetheisa ornatrix in Chapter 17) or groups (such as small ermine moths in Chapter 13 or heliothine moths in Chapter 21). These sections allow the reader to learn about specific examples of the different models of pheromone evolution in moths, the possible mechanisms that lead to reproductive isolation and speciation, and the different inheritance patterns of signal distribution and male preference functions. It is intriguing, for example, that the chemical structures of most common female sex pheromones are restricted to even-numbered chains of 10 to 18 carbons, a few double bonds, and only a few oxygen-containing functional groups, yet the combination of the underlying enzymatic reactions leads to a fascinating diversity of these signals. Equally fascinating is that some of the co-occurring small ermine moth species, for example, do not hybridize even if they share female sex pheromone components, indicating other isolating mechanisms. One of the strengths of the book is that the state of the art of field application (that is, using pheromones for trapping and pest management) is discussed in detail in Part Three. The need to control moth pests has driven basic research and, to some extent, determined which species have received greater attention for investigation. In turn, the increasing ability to identify additional (often minor) pheromone components feeds back into the improvement of trapping efficacy. The history of moth pheromonal communication studies parallels the history of chemical ecology from the very beginning, with the first identification of a pheromone, bombykol, in 1959, but the story is far from over. Only for about 1–2% of the described lepidopteran species do we have chemical identification of the female-produced sex attractant components, and we lack comparative phylogenetic studies for male-produced pheromones. Many of us tend to focus on a certain part of the pheromone mosaic. This book carefully assembles the existing pieces, putting them into an evolutionary perspective and pointing out the gaps in our knowledge that urge us to investigate further.