Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USA.
USDA Forest Service, Interagency Grizzly Bear Study Team, Northern Rockies Science Center, Bozeman, MT 59715, USA.
Environ Entomol. 2023 Apr 18;52(2):230-242. doi: 10.1093/ee/nvad006.
The army cutworm, Euxoa auxiliaris (Grote), is a migratory noctuid that is both an agricultural pest and an important late-season food source for grizzly bears, Ursus arctos horribilis (Linnaeus, Carnivora: Ursidae), within the Greater Yellowstone Ecosystem. Beyond the confirmation of the moths' seasonal, elevational migration in the mid-1900s, little else has been documented about their migratory patterns. To address this missing ecological component, we examined (1) migratory routes during their spring and fall migratory periods throughout their natal range, the Great Plains, and (2) natal origin at two of their summering ranges using stable hydrogen (δ2H) analyses of wings from samples collected within the areas of interest. Stable carbon (δ13C) and stable nitrogen (δ15N) analyses of wings were used to evaluate larval feeding habits of the migrants and agricultural intensity of natal origin sites, respectively. Results suggest that, rather than migrating exclusively east to west, army cutworm moths are also migrating north to south during their spring migration. Moths did not exhibit natal origin site fidelity when returning to the Great Plains. Migrants collected from the Absaroka Range had the highest probability of natal origin in Alberta, British Columbia, Saskatchewan, the most southern region of the Northwest Territories, and second highest probability of origin in Montana, Wyoming, and Idaho. Migrants collected in the Lewis Range had the highest probability of origin in the same provinces of Canada. Results suggest that migrants of the Absaroka Range fed exclusively on C3 plants as larvae and rarely fed in heavily fertilized agroecosystems.
军队毛虫，Euxoa auxiliaris（Grote），是一种迁徙性夜蛾，既是农业害虫，也是大黄石生态系统中灰熊 Ursus arctos horribilis（Linnaeus，Carnivora：Ursidae）重要的晚季食物来源。除了在 20 世纪中期确认了蛾类季节性的海拔迁徙之外，关于它们的迁徙模式几乎没有其他记录。为了解决这个缺失的生态组成部分，我们检查了（1）它们在春、秋迁徙期间在出生地大平原的迁徙路线，以及（2）在两个夏季栖息地的出生地起源，使用收集的翅膀的稳定氢（δ2H）分析感兴趣的区域内的样本。翅膀的稳定碳（δ13C）和稳定氮（δ15N）分析分别用于评估迁徙者的幼虫摄食习惯和出生地起源地的农业强度。结果表明，军队毛虫蛾类在春季迁徙期间不仅向东向西迁徙，还向北向南迁徙。当返回大平原时，蛾类没有表现出出生地起源地的忠诚度。从阿萨巴罗卡山脉收集的迁徙者最有可能在艾伯塔省、不列颠哥伦比亚省、萨斯喀彻温省、西北地区最南部地区以及蒙大拿州、怀俄明州和爱达荷州的第二高起源地出现。从刘易斯山脉收集的迁徙者最有可能在加拿大的相同省份起源。结果表明，阿萨巴罗卡山脉迁徙者的幼虫仅以 C3 植物为食，很少在高度施肥的农业生态系统中觅食。
