Volume 45 - December 2013 : Hawaiian Entomological Society
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ItemThe Importance of Insect Monitoring to Conservation Actions in Hawaii(Hawaiian Entomological Society, 2013-12)Endemic insect species make up the overwhelming majority of Hawaii’s native fauna, and play many important ecological roles. Despite this, insects receive low levels of conservation funding, likely due to their small size, fluctuating popula- tion sizes, and lack of baseline data necessary to determine if they are threatened with extinction. To determine which insects are at risk, how insect populations fluctuate in natural areas, and which management actions are most beneficial to Hawaiian ecosystems, we propose that insects be monitored whenever possible. Insect monitoring should be broad, generating community-based metrics such as species richness, rather that focusing on individual species. Resultant data should be entered into a stable, central database. Rather than individual insect species being the explicit target of conservation, we emphasize that measures of insect diversity can provide an assessment of restoration efforts, and serve as a metric for prioritizing areas for conservation. We provide lists of additional recommenda- tions for land managers and research entomologists who wish to assist with insect conservation efforts.
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ItemKoa Looper Caterpillars (Scotorythra paludicola, Geometridae) Have Lower Fitness on Koa (Acacia koa, Fabaceae) True Leaves than on Phyllodes(Hawaiian Entomological Society, 2013-12)Native plant-herbivore interactions on islands remain understudied due to the widely discussed idea that island plants have weaker defenses than their con- tinental relatives. In Hawaii, the native moth Scotorythra paludicola, a specialist on the native Acacia koa, can undergo outbreaks that defoliate tens of thousands of acres of native koa forest, sometimes leading to massive stand mortality. Such extreme herbivory events are expected to exert strong selection pressure for defense in A. koa. Because mature A. koa trees often re-flush juvenile true leaves after defoliation, we predict that true leaves are better defended against S. paludicola than phyllodes, consistent with the phenomenon of induced resistance. A no-choice bioassay was conducted in the laboratory to compare S. paludicola development on true leaves vs. phyllodes. Consistent with our predictions, caterpillars reared on true leaves had a significantly higher mortality rate and took longer to pupate than caterpillars reared on phyllodes. Additional sources of variation in S. paludicola development included sex, phyllode age (young vs. mature), and host tree identity. Further research is needed to determine the mechanistic traits underlying A. koa resistance to S. paludicola, and to test whether true leaf development does in fact contribute to a reduction in S. paludicola performance and population stability on previously defoliated trees.
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ItemDefoliation of the Invasive Tree Falcataria moluccana on Hawaii Island by the Native Koa Looper Moth (Geometridae: Scotorythra paludicola), and Evaluation of Five Fabaceous Trees as Larval Hostplants(Hawaiian Entomological Society, 2013-12)The koa looper (Geometridae: Scotorythra paludicola) is an endemic Hawaiian moth whose caterpillars feed on Acacia koa, and experience occasional outbreaks, producing vast defoliations of forests. During an extensive and ongoing outbreak of this species on the island of Hawaii, patchy defoliation of Falcataria moluccana (“albizia”) was observed in the vicinity of Akaka Falls State Park, relatively distant from the main defoliation of koa, raising questions about the host range of the koa looper. To identify suitable host plants in the laboratory, we of- fered the koa looper foliage from five fabaceous tree species (A. koa, A. confusa, F. moluccana, Prosopis pallida, and Leucaena leucocephala), and recorded feeding and performance on these diets. Among the five tree species, only A. koa and F. moluccana were accepted as food; caterpillars on the other three species all died by the fifth day of the trial. Survival of the koa looper to pupation and adulthood on F. moluccana did not differ significantly from that on A. koa phyllodes, indicating that this tree is a suitable host, though it does not appear to be widely utilized in the field. Both oviposition preference and larval requirements are likely important determinants of the realized diet breadth for the koa looper. Additionally, develop- ment times at 19°C on A. koa and F. moluccana were nearly twice as long as at 23°C, highlighting the importance of temperature for development of this insect.
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ItemMale Lures and the Detection of Bactrocera Fruit Flies (Diptera: Tephritidae): Performance of Solid Dispensers with Separate Insecticidal Strips Relative to Standard Liquid Lures(Hawaiian Entomological Society, 2013-12)Detection of pestiferous Bactrocera fruit flies (Diptera: Tephritidae) relies largely on deployment of traps baited with male-specific attractants. Two species in particular, B. dorsalis (Hendel) and B. cucurbitae (Coquillett), pose seri- ous threats to US agriculture, and males of these species are attracted to methyl eugenol (ME) and cue lure (CL), respectively. At present, these lures are applied as liquids (with naled added as an insecticide) to cotton wicks placed inside Jackson traps, a procedure that entails considerable handling time and potential health risk owing to inadvertent contact with the chemicals. Recent studies have demonstrated that solid dispensers containing male lures and the toxicant DDVP (dichlorvos) capture as many or more B. dorsalis and B. cucurbitae males as the standard liquid formulation. Owing to registration requirements, deployment of solid dispensers requires the lure and the killing agent be presented in separate devices. The goal of this study was to compare capture of Bactrocera males between traps baited with the liquid formulation (lure and naled mixed) versus traps baited with solid lure-bearing plugs or wafers and separate DDVP strips (lure and DDVP separate). Field trapping was conducted in various areas of Oahu, Hawaii, using variable amounts of DDVP (0.09 – 0.295 g) in the traps with the solid dispensers. In gen- eral, for both B. cucurbitae and B. dorsalis, traps with wafers performed as well as traps with liquids regardless of lure age (fresh or aged 6 weeks), DDVP dose, test location, or lure presentation (ME and CL presented singly or combined). Traps with aged plugs also performed as well as aged liquids for both Bactrocera species under nearly all test conditions. However, in a large proportion of tests, fresh plugs captured significantly fewer males of both species than fresh liquids over the full range of DDVP doses tested. The implications of these findings for Bactrocera detection are discussed.
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ItemHost Plant Records for Fruit Flies (Diptera: Tephritidae: Dacini) in the Pacific Islands: 2. Infestation Statistics on Economic Hosts(Hawaiian Entomological Society, 2013-12)Detailed host records are listed for 39 species of Bactrocera and 2 species of Dacus fruit flies, infesting 98 species of commercial and edible fruits in the Pacific Island Countries and Territories, based on sampling and incubating in laboratory almost 13,000 field collected samples, or over 380,000 fruits. For each host-fly-country association, quantitative data are presented on the weight and number of fruits collected, the proportion of infested samples, the number of adult flies emerged per kg of fruits and, whenever available, the percentage of individual fruits infested. All the published records of each fly-host-country association are cited and erroneous or dubious published records are rectified or commented. Laboratory forced infestation data are also cited and reviewed.