Interactions of adult stoneflies (Plecoptera) with riparian zones I. Effects of air temperature and humidity on longevity

The effects of constant air temperature and relative humidity on the longev ity of three species of gripopterygid stonefly adults from New Zealand were investigated in laboratory experiments, and the results were compared to f ield measurements of air temperature and humidity obtained during summer. G reatest longevity for Zelandobius furcillatus, Zelandoperla decorata and Ac roperla trivacuata was recorded in cool humid conditions (10 degrees C, 100 % humidity) for adults fed water and a 5% sucrose solution. Absence of feed ing reduced survival by 37-73% at 17 degrees C and 100% humidity. Survival decreased significantly with increasing constant air temperature (10, 17 an d 25 degrees C) and decreasing mean relative humidity (100, 81 and 15%). Ma les survived significantly longer than females in all temperature treatment s for Z. furcillatus, but longevity was not influenced by gender in other s pecies or in the humidity experiments. Interpolated LT50 values over 96 h f or female stoneflies in the temperature treatments averaged of 22-23 degree s C. Field measurements at near-ground level and 1.5 m above the streambank during summer indicated that these air temperatures were exceeded for 25% of the time in a pasture catchment compared to <0.1% of the time in a nativ e forest catchment. These findings implicate air temperature as a factor po tentially influencing the longevity of adult stoneflies, and suggest that m aintenance of appropriate microclimate conditions should be a consideration in riparian management.