McPherson M, Shostak A W, Samuel W M
Department of Biological Sciences, University of Alberta, Edmonton, Canada.
J Med Entomol. 2000 Jan;37(1):114-20. doi: 10.1603/0022-2585-37.1.114.
Larvae of winter ticks, Dermacentor albipictus (Packard), ascend vegetation in autumn and form clumps that attach to passing ungulate hosts. We tested the hypothesis that vegetation height determines the height of clumps. During the vegetation-to-ungulate transmission period (early September to mid-November), larvae were released at the base of simulated vegetation (nylon rods 245 cm tall) in outdoor and laboratory trials and in the absence of host cues. Rod height exceeded the height of the tallest ungulate host, which is the moose, Alces alces (L.). Most larvae stopped climbing and formed clumps 50-190 cm above ground, which coincided with torso heights of moose; elk, Cervus elaphus L.; and deer, Odocoileus spp. Rafinesque. More clumps formed in outdoor trials than in laboratory trials and clump heights tended to increase over the course of the experiment, but clump number, size, and height did not correlate with weather conditions. Winter tick larvae appear to determine their height above ground in the absence of external cues, but this mechanism may be modified by external conditions.
冬季硬蜱（Dermacentor albipictus (Packard)）的幼虫在秋季爬上植被并形成团块，附着在路过的有蹄类宿主身上。我们检验了植被高度决定团块高度这一假设。在植被到有蹄类动物的传播期（9月初至11月中旬），在室外和实验室试验中，且在没有宿主线索的情况下，将幼虫释放到模拟植被（245厘米高的尼龙杆）底部。杆的高度超过了最高的有蹄类宿主——驼鹿（Alces alces (L.)）的高度。大多数幼虫停止攀爬并在离地面50 - 190厘米处形成团块，这与驼鹿、马鹿（Cervus elaphus L.）和鹿（Odocoileus spp. Rafinesque）的躯干高度一致。室外试验中形成的团块比实验室试验中的多，并且在实验过程中团块高度有增加的趋势，但团块数量、大小和高度与天气条件无关。冬季硬蜱幼虫似乎在没有外部线索的情况下确定其离地面的高度，但这种机制可能会受到外部条件的影响。
