Volume 56: 2024 - Hawaiian Entomological Society

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    Elucidating the Distribution of Mosquitoes (Diptera: Culicidae) on the Island of Maui
    (2024-10-21) Seaborn, Priscilla; Spafford, Helen; Medeiros, Matthew; Goff, M Lee
    Mosquito-borne diseases are a global threat to public health and wildlife conservation. Avian malaria devastates endemic birds, while introduced mosquitoes in Hawai‘i have caused dengue outbreaks, notably in 2015 on Hawai‘i island, and raise the risk of future arbovirus transmission. This highlights the importance of surveying mosquito populations and creating distribution maps for vector control, especially in neglected areas of Hawai‘i. Currently, there are seven introduced mosquito species in Hawai‘i, six of which are blood-feeding, and five are competent disease vectors. However, the impact of space, time, and elevation on mosquito abundance and species diversity remains unassessed on Maui. This project aimed to fill this gap by characterizing mosquito distribution on Maui using traps deployed around the island for a year. Ae. albopictus was found to be abundant and widely distributed, while Culex quinquefasciatus was abundant but had a limited distribution compared to Ae. albopictus. Ae. vexans and Wy. mitchellii were also collected. June had the highest mosquito capture rate. Hawai‘i faces ongoing threats from new species due to high tourism and cargo shipments, with climate change expected to alter mosquito suitability at higher elevations. This study serves as an important reference for monitoring such changes.
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    Efficacy and Non-target Risks of Broadcasting Amdro Ant Bait to Protect Hawaiian Picture-winged Fly Breeding Habitats
    (2024-10-21)
    Multiple species of rare and federally endangered Hawaiian picturewinged Drosophila flies are at risk from predation by invasive ants, with Solenopsis papuana being the main ant of concern in mesic montane forests on Oʻahu. Prior work demonstrated that suppression of S. papuana with Amdro Ant Block Home Perimeter Ant Bait, distributed in bait stations throughout forest plots, can greatly increase reproductive success of picture-winged flies. The present study tested the efficacy and safety of broadcasting this bait, which is far easier and cheaper. A single broadcast application of Amdro bait at the label rate in 20 x 20 m field plots was very effective for suppressing S. papuana abundances for a period of at least six months, with somewhat weaker effects persisting for up to one year. Broadcast of Amdro bait did not appear to have strong negative impacts on nontarget invertebrates in these forests at the scale investigated: no significant declines were detected in Amdro-treated plots for any taxonomic group either immediately after application or six months later. Furthermore, cage trials suggest that picturewinged flies themselves are not strongly attracted to Amdro bait. Only a single brief feeding episode was observed among 23 flies of three non-listed surrogate species tested, and there was no difference in time to death between flies placed in cages provisioned with Amdro and flies placed in control cages. Collectively, the results suggest that a single broadcast of Amdro is effective for long-term suppression of S. papuana and should pose little risk to non-target ground-dwelling mesic forest invertebrate communities as well as to picture-winged flies.