The monarch butterfly (Danaus plexippus) is a conspicuous insect that has experienced a drastic population decline over the past two decades. While there are several factors contributing to dwindling monarch populations, habitat loss is considered the most significant threat to monarchs. In the United States, loss of milkweed, particularly in the Midwest, has greatly reduced the available breeding habitat of monarchs. This has led to extensive efforts to conserve and restore milkweed resources throughout the Midwest. Recently, these research and conservation efforts have been expanded to include other important areas along the monarch’s migratory path. During the fall of 2018, we conducted surveys of monarch eggs and larvae through West Texas. We documented monarch and queen butterfly (Danaus gilippus) reproduction throughout the region and used the proportion of monarch and queen larva to estimate the number of monarch eggs. Peak egg densities for monarchs were as high as 0.78 per milkweed ramet after correction for the presence of queens. Despite our observations encompassing only a limited sample across one season, the peak monarch egg densities we observed exceeded published reports from when monarch populations were higher. To our knowledge, this is the first study to correct for the presence of queens when calculating the density of monarch eggs. This research also provides insight into monarch utilization of less well-known regions, such as West Texas, and highlights the need to expand the scope of monarch monitoring and conservation initiatives. While the importance of monarch research and conservation in the Midwest is unquestionable, more comprehensive efforts may identify new priorities in monarch conservation and lead to a more robust and effective overall strategy, particularly given the dynamic and rapidly changing global environment.

中文翻译：

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2018年秋季，西德克萨斯州的帝王蝶（Danaus plexippus）和女王蝶（Danaus gilippus）盛行。

帝王蝶（Danaus plexippus）是一种明显的昆虫，在过去的20年中种群数量急剧下降。尽管有许多因素导致君主人口减少，但栖息地的丧失被认为是对君主的最大威胁。在美国，马利筋的流失，特别是在中西部，已经大大减少了君主可利用的繁殖地。这导致了在整个中西部地区保存和恢复乳草资源的广泛努力。最近，这些研究和保护工作已扩大到包括君主迁徙道路上的其他重要地区。在2018年秋季，我们对整个西德克萨斯州的帝王卵和幼虫进行了调查。我们记录了整个地区的帝王蝶和皇后蝴蝶（Danaus gilippus）繁殖，并使用帝王蝶和皇后幼虫的比例来估算帝王卵的数量。校正皇后的出现后，君主的峰值卵子密度高达每乳草分株0.78。尽管我们的观察仅涵盖一个季节的有限样本，但我们观察到的帝王卵密度峰值超过了帝王种群数量较高时的已发布报告。据我们所知，这是第一个在计算帝王蛋密度时纠正皇后存在的研究。这项研究还提供了对不太知名的地区（例如西德克萨斯州）君主利用的见解，并强调了扩大君主监视和保护计划范围的必要性。