Results of the 2006 Wekiu bug (Nysius wekiuicola) surveys on Mauna Kea, Hawaii island: final report
- Author:
-
Englund, R. A., Vorsino, A. E., Laederich, H. M.
- Title:
- Results of the 2006 Wekiu bug (Nysius wekiuicola) surveys on Mauna Kea, Hawaii island: final report
- Year:
- 2007
- Subject:
-
Wekiu bug surveys
Nysius wekiuicola
- Summary:
- As part of a continuing long-term study, the Hawaii Biological Survey of the Bishop Museum was contracted by the Office of Mauna Kea Management (OMKM) to continue its study of the distribution and habitat use of the wekiu bug (Nysius wekiuicola Ashlock and Gagne), which is endemic to the Mauna Kea summit area. Two ten-day field trips to study wekiu bug ecology and distribution occurred in April and May 2006. Another week-long field trip was conducted in October 2006 to retrieve data from temperature loggers that had been installed various locations throughout the Mauna Kea summit in 2005. Along with collecting wekiu bug distribution and temperature data, a trapping study continued to determine whether current or historical trapping methods influence wekiu bug catch effectiveness. Ethylene glycol traps (similar to traps used in earlier studies) and shrimp pitfall traps have been placed in a pairwise fashion at the summit of Puu Hau Kea since 2002. In contrast to the pitfall trapping tests conducted since 2002 that had relatively similar results, ethylene glycol traps were much more effective, with 43 wekiu bugs captured in glycol traps in both April-May 2006 as compared to only one captured in shrimp traps during the same time period. Because much of the snow had not melted by the end of April 2006, no wekiu bugs were collected in any type of trap during the April testing. Because these results were so dramatic and the glycol traps have proven to be so effective, the pitfall trapping test has now been terminated. In 2006 sample effort for wekiu bugs reached an all time high, with 1048 trap days compared to the previous high of 911 trap days in 2005. The major findings of this study were that the snowy winter of 2005-2006 created ideal conditions for a long-lasting snowpack that appeared to provide favorable conditions for wekiu bugs. It was previously postulated that an increased snowpack will favor wekiu bugs because a long-lasting snowpack will provide greater long-term forage opportunities for the eolian drift insects preserved in the snow. Wekiu bug captures from the 2006 field season appear to confirm this hypothesis, as a record number (114 individuals) were either observed or collected around snowbank areas. It was also found that wekiu bug activity did not start until 10 days had elapsed after a large series of snow storms that ended on April 2, 2006. When observing wekiu bugs was started on April 13, 2006, much of the snow had melted except for large patches around the summit areas. That none were collected in traps during our April 2006 field trip despite intensive trapping efforts and visual observations, indicated that wekiu bugs remain inactive for some time after a period of heavy snow. The bugs must have penetrated fairly deep into the substrate to get away from the surface layer of snow that was over 2-3 m thick drifts in many summit areas. During the 2006 field season, the nunatak hypothesis postulated by Porter and Englund (2006) for wekiu bug distribution was successfully tested. This hypothesis states wekiu bug distribution is related to topography, and that wekiu bugs currently inhabit only areas of the summit that represented ice-free refugia inside the limit of the glacial ice cap that reached its maximum size about 20,000 years ago, and disappeared by about 16,500 years ago. By examining the geology of unsampled cinder cones, and also unsampled areas of previously sampled cones, a predictive list was compiled for environmentally promising habitats to sample for additional bug populations. Several significant and new bug populations were found using these predictions, most notably in areas adjacent to the VLBA facility and areas around the adze quarry.
- URL:
- http://hbs.bishopmuseum.org/pdf/wekiu2007low.pdf
- Date:
- April 2007
- Collection:
- Monographs