Annual Review of Entomology - Volume 59, 2014

Many farmers rely on regular pesticide applications to avoid losses from arthropod pests and the diseases they vector. However, widespread and injudicious use of pesticides is detrimental to the environment, poses a health risk, and undermines biocontrol services. Researchers are increasingly required to develop techniques to quantify the trade-offs and risks associated with pesticides. Laboratory studies, though useful for assessing short-term impacts (e.g., mortality), cannot detect longer-term or indirect effects that can potentially be assessed using semifield studies. Here we review the range and scope of studies that have used semifield methods for regulatory testing and risk assessment of pesticides and for understanding the community-level effects of pesticide use in agricultural landscapes. We include studies on target and nontarget species, with an emphasis on quantifying effects when the target species is highly mobile. We suggest improvements in the design and analysis of semifield studies to more effectively assess effects on highly mobile species.

Oenocytes have intrigued insect physiologists since the nineteenth century. Many years of careful but mostly descriptive research on these cells highlights their diverse sizes, numbers, and anatomical distributions across Insecta. Contemporary molecular genetic studies in Drosophila melanogaster and Tribolium castaneum support the hypothesis that oenocytes are of ectodermal origin. They also suggest that, in both short and long germ-band species, oenocytes are induced from a Spalt major/Engrailed ectodermal zone by MAPK signaling. Recent glimpses into some of the physiological functions of oenocytes indicate that they involve fatty acid and hydrocarbon metabolism. Genetic studies in D. melanogaster have shown that larval oenocytes synthesize very-long-chain fatty acids required for tracheal waterproofing and that adult oenocytes produce cuticular hydrocarbons required for desiccation resistance and pheromonal communication. Exciting areas of future research include the evolution of oenocytes and their cross talk with other tissues involved in lipid metabolism such as the fat body.

Sexual selection has resulted in some of the most captivating features of insects, including flashy colors, bizarre structures, and complex pheromones. These features evolve in dynamic environments, where conditions can change rapidly over space and time. However, only recently has ecological complexity been embraced by theory and practice in sexual selection. We review replicated selection studies as well as studies on variation in the agents of selection to delineate gaps in current knowledge and clarify exciting new directions for research. Existing work suggests that fluctuations in sexual selection may be extremely common, though work on the ecological factors influencing these fluctuations is scarce. We suggest that deeper ecological perspectives on sexual selection may alter some of the fundamental assumptions of sexual selection theory and rapidly lead to new discoveries.

The poultry red mite, Dermanyssus gallinae, poses a significant threat to poultry production and hen health in many parts of the world. With D. gallinae increasingly suspected of being a disease vector, and reports indicating that attacks on alternative hosts, including humans, are becoming more common, the economic importance of this pest has increased greatly. As poultry production moves away from conventional cage systems in many parts of the world, D. gallinae is likely to become more abundant and difficult to control. Control remains dominated by the use of synthetic acaricides, although resistance and treatment failure are widely reported. Alternative control measures are emerging from research devoted to D. gallinae and its management. These alternative control measures are beginning to penetrate the market, although many remain at the precommercial stage. This review compiles the expanding body of research on D. gallinae and assesses options for its current and future control. We conclude that significant advances in D. gallinae control are most likely to come through an integrated approach adopting recent research into existing and novel control strategies; this is being combined with improved monitoring and modeling to better inform treatment interventions.

Lineages of insect pathogenic fungi are concentrated in three major clades: Hypocreales (several genera), Entomophthoromycota (orders Entomophthorales and Neozygitales), and Onygenales (genus Ascosphaera). Our review focuses on aspects of the evolutionary biology of these fungi that have remained underemphasized in previous reviews. To ensure integration with the better-known domains of insect pathology research, we followed a conceptual framework formulated by Tinbergen, asking complementary questions on mechanism, ontogeny, phylogeny, and adaptation. We aim to provide an introduction to the merits of evolutionary approaches for readers with a background in invertebrate pathology research and to make the insect pathogenic fungi more accessible as model systems for evolutionary biologists. We identify a number of questions in which fundamental research can offer novel insights into the evolutionary forces that have shaped host specialization and life-history traits such as spore number and size, somatic growth rate, toxin production, and interactions with host immune systems.

The orb-weaving spiders (Orbiculariae) comprise more than 25% of the approximately 44,000 known living spider species and produce a remarkable variety of webs. The wheel-shaped orb web is primitive to this clade, but most Orbiculariae make webs hardly recognizable as orbs. Orb-weavers date at least to the Jurassic. With no evidence for convergence of the orb web, the monophyly of the two typical orb web taxa, the cribellate Deinopoidea and ecribellate Araneoidea, remains problematic, supported only weakly by molecular studies. The sister group of the Orbiculariae also remains elusive. Despite more than 15 years of phylogenetic scrutiny, a fully resolved cladogram of the Orbiculariae families is not yet possible. More comprehensive taxon sampling, comparative morphology, and new molecular markers are required for a better understanding of orb-weaver evolution.

Significant progress has been achieved in silkworm (Bombyx mori) research since the last review on this insect was published in this journal in 2005. In this article, we review the new and exciting progress and discoveries that have been made in B. mori during the past 10 years, which include the construction of a fine genome sequence and a genetic variation map, the evolution of genomes, the advent of functional genomics, the genetic basis of silk production, metamorphic development, immune response, and the advances in genetic manipulation. These advances, which were accelerated by the genome sequencing project, have promoted B. mori as a model organism not only for lepidopterans but also for general biology.

The interactions among insects, mites, and fungi are diverse and complex but poorly understood in most cases. Associations among insects, mites, and fungi span an almost incomprehensible array of ecological interactions and evolutionary histories. Insects and mites often share habitats and resources and thus interact within communities. Many mites and insects rely on fungi for nutrients, and fungi benefit from them with regard to spore dispersal, habitat provision, or nutrient resources. Mites have important impacts on community dynamics, ecosystem processes, and biodiversity within many insect-fungus systems. Given that mites are understudied but highly abundant, they likely have bigger, more important, and more widespread impacts on communities than previously recognized. We describe mutualistic and antagonistic effects of mites on insect-fungus associations, explore the processes that underpin ecological and evolutionary patterns of these multipartite communities, review well-researched examples of the effects of mites on insect-fungus associations, and discuss approaches for studying mites within insect-fungus communities.

Entomophagous arthropods can provide valuable biological control services, but they need to fulfill their life cycle in agricultural landscapes often dominated by ephemeral and disturbed habitats. In this environment, movement is critical to escape from disturbances and to find resources scattered in space and time. Despite considerable research effort in documenting species movement and spatial distribution patterns, the quantification of arthropod movement has been hampered by their small size and the variety of modes of movement that can result in redistribution at different spatial scales. In addition, insight into how movement influences in-field population processes and the associated biocontrol services is limited because emigration and immigration are often confounded with local-scale population processes. More detailed measurements of the habitat functionality and movement processes are needed to better understand the interactions between species movement traits, disturbances, the landscape context, and the potential for entomophagous arthropods to suppress economically important pests.