Male-Produced Sex Pheromone of the Carrion Beetles, Oxelytrum discicolle and its Attraction to Food Sources

Recent advances in the synthesis of insect pheromones: an overview from 2013 to 2022

Covering: 2013 to June 2022Pheromones are usually produced by insects in sub-microgram amounts, which prevents the elucidation of their structures by nuclear magnetic resonance (NMR). Instead, a synthetic reference material is needed to confirm the structure of the natural compounds. In addition, the provision of synthetic pheromones enables large-scale field trials for the development of environmentally friendly pest management tools. Because of these potential applications in pest control, insect pheromones are attractive targets for the development of synthetic procedures and the synthesis of these intraspecific chemical messengers has been at the core of numerous research efforts in the field of pheromone chemistry. The present review is a quick reference guide for the syntheses of insect pheromones published from 2013 to mid-2022, listing the synthesized compounds and highlighting current methodologies in organic synthesis, such as carbon-carbon coupling reactions, organo-transition metal chemistry including ring-closing olefin metathesis, asymmetric epoxidations and dihydroxylations, and enzymatic reactions.

Relative Insect Frequency and Species Richness on Sun-Exposed and Shaded Rabbit Carrions

On rabbit carcasses (Oryctolagus cuniculus L.) exposed in open and shaded habitats, the relative abundance of insects and species richness were observed. The decomposition process was classified into four stages: fresh, bloated, decayed, and dry. Except for the decayed stage, the elapsed time for each stage of decomposition was similar between open and shaded habitats, with all carcasses reaching dryness in 13 and 14 d, respectively. In total, 2009 insects were collected during the decomposition process with 1,863 flies belonging to seven families and 15 species, and 146 beetles belonging to six species and three families. Insect abundances rose between the fresh and decay stages. The dominant families of insects included Calliphoridae and Muscidae (80.9% of the collected insects) and accounting for 38.07% of the species richness, whereas Histeridae accounted for 4.3% of the collected insects and 14.29% of the species richness. The open habitat attracted 1,233 insects belonging to 18 families, including 1,142 flies and 91 beetles, whereas the shaded habitat attracted 776 insects belonging to 18 families, including 721 flies and 55 beetles. Diversity level and ratios of exclusive species are also reported for each habitat (open 61.4%; shaded 38.6%). Between habitats, there were substantially separate insect communities, however. In addition, there was a substantial difference in the insect number and species between decomposition stages. This study demonstrates that the exposure status needs to be evaluated and examined when estimating the time since death.

Alkene Synthesis by Photocatalytic Chemoenzymatically Compatible Dehydrodecarboxylation of Carboxylic Acids and Biomass

Direct conversion of renewable biomass and bioderived chemicals to valuable synthetic intermediates for organic synthesis and materials science applications by means of mild and chemoselective catalytic methods has largely remained elusive. Development of artificial catalytic systems that are compatible with enzymatic reactions provides a synergistic solution to this enduring challenge by leveraging previously unachievable reactivity and selectivity modes. We report herein a dual catalytic dehydrodecarboxylation reaction that is enabled by a crossover of the photoinduced acridine-catalyzed O-H hydrogen atom transfer (HAT) and cobaloxime-catalyzed C-H-HAT processes. The reaction produces a variety of alkenes from readily available carboxylic acids. The reaction can be embedded in a scalable triple-catalytic cooperative chemoenzymatic lipase-acridine-cobaloxime process that allows for direct conversion of plant oils and biomass to long-chain terminal alkenes, precursors to bioderived polymers.

Diel Activity and Effect of Carcass Decomposition on the Attractiveness to the Forensically Important Species Oxelytrum Discicolle (Coleoptera: Silphidae)†

Oxelytrum discicolle is a carrion beetle commonly found in the Neotropical region, mainly associated with cadavers and carcasses. Information on behavior related to the likelihood of cadaver colonization is scarce. We performed two field experiments in peri-urban forest in Brazil in order to strengthen our knowledge on O. discicolle behavior. In the first experiment, we assessed the preference for piglet carcasses at different stages of decomposition offered simultaneously in two seasons, dry and rainy, while in the second experiment we investigated the diel activity of adults. A total of 493 adults were collected in the experiments. A significantly higher abundance was detected in the rainy season. There was a marked preference for carcasses at advanced stages. Adults exhibited a typical nocturnal behavior, the number trapped at night was 17 times greater than those collected during the day. Oxelytrum discicolle is nocturnal species that prefers carcasses in advanced stage of decomposition.

Beyond Cuticular Hydrocarbons: Chemically Mediated Mate Recognition in the Subsocial Burying Beetle Nicrophorus vespilloides

Burying beetles have fascinated scientists for centuries due to their elaborate form of biparental care that includes the burial and defense of a vertebrate carcass, as well as the subsequent feeding of the larvae. However, besides extensive research on burying beetles, one fundamental question has yet to be answered: what cues do males use to discriminate between the sexes? Here, we show in the burying beetle Nicrophorus vespilloides that cuticular lipids trigger male mating behavior. Previous chemical analyses have revealed sex differences in cuticular hydrocarbon (CHC) composition; however, in the current study, fractionated-guided bioassay showed that cuticular lipids, other than CHCs, elicit copulation. Chemical analyses of the behaviorally active fraction revealed 17 compounds, mainly aldehydes and fatty acid esters, with small quantitative but no qualitative differences between the sexes. Supplementation of males with hexadecanal, the compound contributing most to the statistical separation of the chemical profiles of males and females, did not trigger copulation attempts by males. Therefore, a possible explanation is that the whole profile of polar lipids mediates sex recognition in N. vespilloides.