Robert F. Mitchell

Treating Panel Traps with a Fluoropolymer Enhances their Efficiency in Capturing Cerambycid Beetles

ABSTRACT The most effective traps for capturing cerambycids and other saproxylic beetles are intercept designs such as funnel traps and cross-vane panel traps. We have observed that adult cerambycids of many species often alight and walk upon panel traps, and few are actually captured. In an effort to improve trap capture and retention, researchers have treated intercept traps with Rain-X, a polysiloxane formulation that renders surfaces more slippery. Here, we summarize experiments that compared the efficacies of Rain-X and Fluon, a PTFE fluoropolymer dispersion, as surface treatments for panel traps that are deployed to capture cerambycid beetles, using untreated traps as controls. Fluon-treated traps captured on average >14× the total number of beetles, and many more cerambycid species, than were captured by Rain-X-treated or control traps. Beetles captured by Fluon-treated traps ranged in body length by 350%. They could not walk on vertical panels treated with Fluon but easily walked on those treated with Rain-X and on untreated traps. Moreover, a single Fluon treatment remained effective for the entire field season, even in inclement weather. We conclude that treating panel traps with Fluon greatly improves their efficiency in capturing cerambycid beetles. This increased efficacy will be particularly important when traps are deployed to detect very low-density populations, such as incursions of exotic species, or remnant communities of rare and endangered species. The influence of Fluon on trap efficiency may vary with product formulation and its source and also with climatic conditions.

Causes and Consequences of Cannibalism in Noncarnivorous Insects

We review the primary literature to document the incidence of cannibalism among insects that typically are not carnivorous. Most of the cannibalistic species were coleopterans and lepidopterans, and the cannibals often were juveniles that aggregate or that overlap in phenology with the egg stage. Cannibalism can be adaptive by improving growth rate, survivorship, vigor, longevity, and fecundity. It also can play an important role in regulating population density and suppressing population outbreaks, stabilizing host plant-insect relationships, and reducing parasitism rates. Cannibalism often was favored by density-dependent factors for herbivores that feed in concealed feeding situations (such as stem borers, leafminers), but also by density-independent factors (such as high ambient temperature) for herbivores that feed in exposed feeding situations.

The Golgi-Associated Protein p115 Mediates the Secretion of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a leaderless protein that is secreted from cells by a specialized, nonclassical export pathway. The release of MIF nevertheless is regulated and its production in response to different inflammatory, mitogenic, and hormonal stimuli plays an important role in diverse physiologic and pathologic processes. We report herein the identification of the Golgi complex-associated protein p115 as an intracellular binding partner for MIF. MIF interacts with p115 in the cytoplasm and the stimulated secretion of MIF results in the accumulation of both proteins in supernatants, which is consistent with MIF release from cells in conjunction with p115. The depletion of p115 from monocytes/macrophages decreases the release of MIF but not other cytokines following inflammatory stimulation or intracellular bacterial infection. Notably, the small molecule MIF inhibitor 4-iodo-6-phenylpyrimidine inhibits MIF secretion by targeting the interaction between MIF and p115. These data reveal p115 to be a critical intermediary component in the regulated secretion of MIF from monocytes/macrophages.

Sequencing and characterizing odorant receptors of the cerambycid beetle Megacyllene caryae

Odorant receptors (Ors) are a unique family of ligand-gated ion channels and the primary mechanism by which insects detect volatile chemicals. Here, we describe 57 putative Ors sequenced from an antennal transcriptome of the cerambycid beetle Megacyllene caryae (Gahan). The male beetles produce a pheromone blend of nine compovnents, and we functionally characterized Ors tuned to three of these chemicals: receptor McOr3 is sensitive to (S)-2-methyl-1-butanol; McOr20 is sensitive to (2S,3R)-2,3-hexanediol; and McOr5 is sensitive to 2-phenylethanol. McOr3 and McOr20 are also sensitive to structurally-related chemicals that are pheromones of other cerambycid beetles, suggesting that orthologous receptors may be present across many cerambycid species. These Ors are the first to be functionally characterized from any species of beetle and lay the groundwork for understanding the evolution of pheromones within the Cerambycidae.

Fuscumol and fuscumol acetate are general attractants for many species of cerambycid beetles in the subfamily Lamiinae.

(E)‐6,10‐dimethyl‐5,9‐undecadien‐2‐ol (fuscumol) is an important component of male‐produced aggregation pheromones for several species of cerambycid beetles in the genus Tetropium (subfamily Aseminae/Spondylidinae). Here, we describe the experiments that tested the hypothesis that fuscumol and/or fuscumol acetate also are general attractants for species in the cerambycid subfamily Lamiinae. At field sites in northwestern Indiana and central Texas (USA), panel traps baited with fuscumol or its acetate captured 331 lamiine beetles, compared to 11 beetles captured in control traps. Three species were attracted to traps baited with fuscumol as a single component, whereas another four species were attracted to fuscumol acetate alone. Surprisingly, fuscumol acetate also attracted two species in the subfamily Cerambycinae: Xylotrechus colonus (Fabricius) (males of which produce a pheromone composed only of stereoisomers of 2,3‐hexanediol and 3‐hydroxyhexan‐2‐one), and Obrium maculatum (Olivier) (for which a pheromone has yet to be identified). In an independent field experiment in east‐central Illinois (USA), traps baited with fuscumol and/or its acetate captured 136 beetles of eight lamiine species, all but one species of which were also captured in the other experiment. Blending fuscumol and its acetate did not inhibit responses of species to either of the individual compounds, but synergized their activity for one species. Our results support the hypothesis that fuscumol and fuscumol acetate are widespread pheromone components or attractants for a variety of cerambycid species, especially lamiines in the tribe Acanthocinini.

Evolution of herbivory in Drosophilidae linked to loss of behaviors, antennal responses, odorant receptors, and ancestral diet

Significance The evolution of herbivory in animals is rare but has resulted in major adaptive radiations. Its rarity suggests that there are barriers to colonization of plants. Behavioral adaptations, involving host plant finding, are likely the first to evolve during the transition to herbivory. A recently evolved herbivorous fly species was derived from yeast-feeding ancestors. This herbivorous fly, unlike its yeast-feeding relatives, lost attraction to yeast volatiles, the ability to detect yeast volatiles, and three genes that encode olfactory receptors critical for detecting yeast volatiles in Drosophila melanogaster. Loss-of-function mutations may play a role in the transition to herbivory in insects, which account for nearly 25% of all species of life. Herbivory is a key innovation in insects, yet has only evolved in one-third of living orders. The evolution of herbivory likely involves major behavioral changes mediated by remodeling of canonical chemosensory modules. Herbivorous flies in the genus Scaptomyza (Drosophilidae) are compelling species in which to study the genomic architecture linked to the transition to herbivory because they recently evolved from microbe-feeding ancestors and are closely related to Drosophila melanogaster. We found that Scaptomyza flava, a leaf-mining specialist on plants in the family (Brassicaceae), was not attracted to yeast volatiles in a four-field olfactometer assay, whereas D. melanogaster was strongly attracted to these volatiles. Yeast-associated volatiles, especially short-chain aliphatic esters, elicited strong antennal responses in D. melanogaster, but weak antennal responses in electroantennographic recordings from S. flava. We sequenced the genome of S. flava and characterized this species’ odorant receptor repertoire. Orthologs of odorant receptors, which detect yeast volatiles in D. melanogaster and mediate critical host-choice behavior, were deleted or pseudogenized in the genome of S. flava. These genes were lost step-wise during the evolution of Scaptomyza. Additionally, Scaptomyza has experienced gene duplication and likely positive selection in paralogs of Or67b in D. melanogaster. Olfactory sensory neurons expressing Or67b are sensitive to green-leaf volatiles. Major trophic shifts in insects are associated with chemoreceptor gene loss as recently evolved ecologies shape sensory repertoires.

Response of the woodborers Monochamus carolinensis and Monochamus titillator (Coleoptera: Cerambycidae) to known cerambycid pheromones in the presence and absence of the host plant volatile α-pinene.

ABSTRACT In recent years, several attractant pheromones have been identified for cerambycid beetles, including 2-(undecyloxy)-ethanol (hereafter monochamol) for Monochamus galloprovincialis (Olivier), M. alternatus Hope, and M. scutellatus (Say). This study screened eight known cerambycid pheromones or their analogues (including monochamol) as potential attractants for M. carolinensis Olivier and M. titillator (F.), in the presence and absence of the host volatile &agr;-pinene. Monochamol attracted M. carolinensis in the presence and absence of &agr;-pinene, whereas M. titillator was only attracted to the combination of monochamol and &agr;-pinene. (2R*,3R*)-2,3-Hexanediol also attracted both M. carolinensis and M. titillator, but only in the presence of &agr;-pinene. Subsequent coupled gas chromatography—mass spectrometry and gas chromatography—electroantennogram detection analyses of extracts of volatiles collected from both sexes demonstrated that male M. carolinensis and M. titillator release monochamol, and that antennae of males and females of both species detect it. These results indicate that monochamol is a male-produced pheromone for both M. carolinensis and M. titillator.

Genome of the Asian longhorned beetle (Anoplophora glabripennis), a globally significant invasive species, reveals key functional and evolutionary innovations at the beetle-plant interface

BackgroundRelatively little is known about the genomic basis and evolution of wood-feeding in beetles. We undertook genome sequencing and annotation, gene expression assays, studies of plant cell wall degrading enzymes, and other functional and comparative studies of the Asian longhorned beetle, Anoplophora glabripennis, a globally significant invasive species capable of inflicting severe feeding damage on many important tree species. Complementary studies of genes encoding enzymes involved in digestion of woody plant tissues or detoxification of plant allelochemicals were undertaken with the genomes of 14 additional insects, including the newly sequenced emerald ash borer and bull-headed dung beetle.ResultsThe Asian longhorned beetle genome encodes a uniquely diverse arsenal of enzymes that can degrade the main polysaccharide networks in plant cell walls, detoxify plant allelochemicals, and otherwise facilitate feeding on woody plants. It has the metabolic plasticity needed to feed on diverse plant species, contributing to its highly invasive nature. Large expansions of chemosensory genes involved in the reception of pheromones and plant kairomones are consistent with the complexity of chemical cues it uses to find host plants and mates.ConclusionsAmplification and functional divergence of genes associated with specialized feeding on plants, including genes originally obtained via horizontal gene transfer from fungi and bacteria, contributed to the addition, expansion, and enhancement of the metabolic repertoire of the Asian longhorned beetle, certain other phytophagous beetles, and to a lesser degree, other phytophagous insects. Our results thus begin to establish a genomic basis for the evolutionary success of beetles on plants.

Cerambycid Beetle Species with Similar Pheromones are Segregated by Phenology and Minor Pheromone Components

Recent research has shown that volatile sex and aggregation-sex pheromones of many species of cerambycid beetles are highly conserved, with sympatric and synchronic species that are closely related (i.e., congeners), and even more distantly related (different subfamilies), using the same or similar pheromones. Here, we investigated mechanisms by which cross attraction is averted among seven cerambycid species that are native to eastern North America and active as adults in spring: Anelaphus pumilus (Newman), Cyrtophorus verrucosus (Olivier), Euderces pini (Olivier), Neoclytus caprea (Say), and the congeners Phymatodes aereus (Newman), P. amoenus (Say), and P. varius (F.). Males of these species produce (R)-3-hydroxyhexan-2-one as their dominant or sole pheromone component. Our field bioassays support the hypothesis that cross attraction between species is averted or at least minimized by differences among species in seasonal phenology and circadian flight periods of adults, and/or by minor pheromone components that act as synergists for conspecifics and antagonists for heterospecifics.

Insect Frass as a Pathway for Transmission of Bacterial Wilt of Cucurbits

ABSTRACT Insects that vector diseases of plants are of critical concern to agriculture, but relationships between the vectors and pathogens often are poorly understood. In this study, we present research on vector relationships between the striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae), and the pathogen that causes bacterial wilt of cucurbits, Erwinia tracheiphila (Smith) (Enterobacteriales: Enterobacteriaceae). We studied how the bacteria were retained in the gut of the beetle by developing a polymerase chain reaction (PCR)-based technique for extracting and identifying bacterial DNA in the frass. Bacterial DNA usually was present in the frass for 24 h after beetles had consumed inoculum but diminished quickly and was undetectable within 96 h. The amount of time that bacterial DNA could be detected in frass increased with the amount of inoculum and the length of time that beetles were exposed to inoculum and also varied with the strain of bacterium. Frass that tested positive for bacterial DNA also was infective to cucumber plants, confirming that DNA was indicative of viable bacteria and that frass could be a pathway for transmission of the pathogen. This research suggests that few cucumber beetles serve as long-term vectors of the pathogen and that aggregation of the beetle on host plants may be critical for initiating plant infections in spring.