"Neuroethoendocrinology": integration of field and laboratory studies in insect neuroendocrinology

The Biology and Social Life of Earwigs (Dermaptera)

Earwigs are often known for the forceps-like appendage at the end of their abdomen, urban legends about them crawling into human ears, and their roles as pest and biological control agents. However, they are much less known for their social life. This is surprising, as many of the 1,900 species of earwigs show social behaviors toward eggs, juveniles, and adults. These behaviors typically occur during family and group living, which may be obligatory or facultative, last up to several months, and involve only a few to several hundred related or unrelated individuals. Moreover, many individuals can alternate between solitary and group living during their life cycle, an ability that probably prevailed during the emergence of social life. In this review, I detail the diversity of group living and social behavior in earwigs and show how further developing this knowledge in Dermaptera can improve our general understanding of the early evolution of social life in insects.

Lateralization of Courtship Traits Impacts Pentatomid Male Mating Success—Evidence from Field Observations

Simple Summary

Although a growing number of studies have reported asymmetries of brain and behavior in various insect orders, detailed information on lateralization in the courtship and mating behavior of insects in the wild is scarce. In this research, we studied the courtship and mating behavior of the neem bug, Halys dentatus, in the field, quantifying lateralized behavioral displays, and assessing their impact on male mating success. A population-level lateralization in males approaching females was found. Furthermore, the male mating success was affected by lateralization; right-biased males achieved higher mating success rates. Overall, our results add useful knowledge on the reproductive behavior of H. dentatus in the field, with potential applications for identifying useful benchmarks to monitor the quality of individuals mass-reared for pest control purposes over time. This study furtherly highlights the role of lateralized traits in determining male mating success in insects.

Abstract

Lateralization has been documented in many insect species, but limited information on courtship and mating lateralization in wild conditions is available. We conducted field investigation on the courtship and mating behavior of the neem bug, Halys dentatus, a polyphagous insect mainly infesting Azadirachta indica, with particular attention to lateralization of mating displays. We investigated the presence of population-level behavioral asymmetries during H. dentatus sexual interactions and their influence on male mating success. Two lateralized traits were found: left or right-biased male approaches to the female and left or right-biased male turning displays. Males approaching females from their left side were mainly right-biased in the 180° turning display, and males that approached females from their right side were mainly left-biased. Right-biased males by turning 180° to carry out end-to-end genital contact, performed a lower number of copulation attempts, thus starting copula earlier than left-biased males. Mating success was higher when males approached the left side of females during sexual interactions. A higher number of successful mating interactions was observed in right-biased males when turning 180°. Our results add useful knowledge on the reproductive behavior of H. dentatus in the field, with potential applications for identifying useful benchmarks to monitor the quality of individuals mass-reared for pest control purposes over time.

Reduced female mating receptivity and activation of oviposition in two Callosobruchus species due to injection of biogenic amines

Analyses of proximate mechanisms that control mating and oviposition behaviours in insects are important because they link behavioural ecology and physiology. Recently, seed beetles have been used as models to study evolution of female multiple mating and cost of reproduction including mating. In the present study, we investigated the effects of biogenic amines into the abdomens of females of two Callosobruchus species, Callosobruchus chinensis and Callosobruchus maculatus, on mating receptivity and oviposition behaviour. In C. chinensis, injection of octopamine and tyramine reduced receptivity to mating and tyramine and serotonin increased the number of eggs laid. Similarly, injection of tyramine reduced the receptivity of females and increased the number of eggs laid by females of C. maculatus. These results show the possibility that biogenic amines control mating receptivity and oviposition behaviour in females of two Callosobruchus species.

Odorants that induce hygienic behavior in honeybees: identification of volatile compounds in chalkbrood-infected honeybee larvae

Social insects that live in large colonies are vulnerable to disease transmission due to relatively high genetic relatedness among individuals and high rates of contact within and across generations. While individual insects rely on innate immune responses, groups of individuals also have evolved social immunity. Hygienic behavior, in which individual honeybees detect chemical stimuli from diseased larvae and subsequently remove the diseased brood from the nest, is one type of social immunity that reduces pathogen transmission. Three volatile compounds, collected from larvae infected with the fungal pathogen Ascosphaera apis and detected by adult honey bees, were identified by coupled gas chromatography-electroantennographic detection and gas chromatography-mass spectrometry. These three compounds, phenethyl acetate, 2-phenylethanol, and benzyl alcohol, were present in volatile collections from infected larvae but were absent from collections from healthy larvae. Two field bioassays revealed that one of the compounds, phenethyl acetate is a key compound associated with Ascosphaera apis-infected larvae that induces hygienic behavior.

Microarray analysis yields candidate markers for rotation resistance in the western corn rootworm beetle, Diabrotica virgifera virgifera

As pest species may evolve resistance to chemical controls, they may also evolve resistance to cultural control methods. Yearly rotation of corn (Zea mays) with another crop interrupts the life cycle of the western corn rootworm beetle (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), but behavioral resistance to crop rotation is now a major problem in the Midwest of the USA. Resistant adult females exhibit reduced fidelity to corn as a host and lay their eggs in the soil of both corn and soybean (Glycine max) fields. Behavioral assays suggest that the adaptation is related to increased locomotor activity, but finding molecular markers has been difficult. We used microarray analysis to search for gene expression differences between resistant and wild-type beetles. Candidates validated with real-time polymerase chain reaction exhibit predicted patterns from the microarray in independent samples across time and space. Many genes more highly expressed in the rotation-resistant females have no matches to known proteins, and most genes that were more lowly expressed are involved in antimicrobial defense.

Pilocarpine improves recognition of nestmates in young honey bees

Honey bees can distinguish nestmates from non-nestmates, directing aggressive responses toward non-nestmates and rarely attacking nestmates. Here we provide evidence that treatment with pilocarpine, a muscarinic agonist, significantly reduced the number of aggressive responses directed toward nestmates. By contrast, treatment with scopolamine, a muscarinic antagonist, significantly increased attacks on nestmates. Locomotor activity was not altered by these pharmacological treatments. When interpreted in light of known cholinergic pathways in the insect brain, our results provide the first evidence that cholinergic signaling via muscarinic receptors plays a role in olfaction-based social behavior in honey bees.