Results of 2005 Wekiu bug (Nysius Wekiuicola) surveys on Mauna Kea, Hawaii Island. Final report
- Author:
-
Englund, R. A., Vorsino, A. E., Laederich, H. M., Ramsdale, A., McShane, M., Hawaii Biological Survey,
- Title:
- Results of 2005 Wekiu bug (Nysius Wekiuicola) surveys on Mauna Kea, Hawaii Island. Final report
- Year:
- 2006
- Subject:
-
Wekiu bug surveys
Nysius wekiuicola
- Summary:
- This study continues research conducted by the Hawaii Biological Survey of the Bishop Museum beginning in the early 1980s, resuming in 1997, and ongoing since 2002. The objectives of this study were to 1) survey for the presence or absence of wekiu bugs at the summits of various puu’s (cinder cones) located in the alpine zone of Mauna Kea, 2) determine the elevational and microhabitat distribution of wekiu bugs on Mauna Kea, 3) assess whether different pitfall trapping methods used in earlier Bishop Museum studies provide comparable data in regard to wekiu bug captures, 4) assess habitats among different elevations and cinder cone areas, and 5) obtain microhabitat data on wekiu bug habitat using temperature and relative humidity loggers. In 2005, surveys for wekiu bug distribution and abundance at the summit area of Mauna Kea occurred in May and June, while data loggers recording microhabitat parameters such as relative humidity and temperature were installed in December 2004 and data downloaded June 2005. A wide range of areas were surveyed, including several important areas that were previously unsampled, including the area above the Puu Laau cabin in the western summit region, and Puu Lilinoe. Sampling effort in 2005 was the highest to date of the recent studies, with 529 trap days in May and 382 trap days in June, for a total effort of 911 trap days. This compares to 274 trap days in 2004 and 398 trap days in 2002. Important discoveries in 2005 included the finding of a new core wekiu bug population at Puu Lilinoe and the rediscovery of a large population at Puu Poliahu. While both the shrimp pitfall and older style ethylene glycol traps were found to have limitations during the present study, collections of wekiu bugs through visual observations around areas of snowbanks proved exceedingly successful. For example, as many wekiu bugs were collected during 20 minutes of visual observations at the summit of Puu Hau Kea as compared to 9 days of trapping at this cinder cone. The long-term test of trapping efficiency continued to determine whether data from shrimp pitfall traps presently used can be compared to data collected in the original 1982 study using ethylene glycol traps. Although the results remain generally inconclusive, it is apparent that glycol traps attract wekiu bugs in a very efficient manner under certain cases of reduced snow pack, such as in the late spring. On the other hand, there appears to be little difference in trap efficiency such as in May 2005 when a large snowpack was available, or in other seasons having low wekiu bug abundance such as in the warm and dry July 2004. This year marked the first time wekiu bug distribution and temperature patterns at various areas within the Mauna Kea summit were examined. Logger data indicated the summit area is marked by low mean temperatures, wide surface temperature variations, and long periods of ice and snow resulting in much less variation. A transect of loggers at various positions on Puu Hau Kea indicated that the bottom area of this cinder cone has much lower temperatures than are found at the summit regions. Preliminary findings from the data loggers indicate that wekiu bugs may seek areas of thermal stability, such as the summit areas with long-lasting snowbanks. The spring months when wekiu bugs are most active exhibited dramatic daily temperature shifts, with temperatures dropping below freezing on a nightly basis.
- URL:
- http://hbs.bishopmuseum.org/pdf/wekiu2005.pdf
- Date:
- March 2006
- Collection:
- Monographs