Monarch butterfly (Danaus plexippus L.) declines in eastern North America have prompted milkweed host plant restoration efforts in non-agricultural grasslands. However, grasslands harbor predator communities that exert high predation pressure on monarch eggs and larvae. While diurnal monarch predators are relatively well known, no studies have investigated the contribution of nocturnal monarch predators. We used video cameras to monitor sentinel monarch eggs and fourth instars on milkweed in southern Michigan to identify predators and determine if nocturnally-active species impose significant predation pressure. We observed ten arthropod taxa consuming monarch eggs and larvae, with 74% of egg predation events occurring nocturnally. Taxa observed attacking monarch eggs included European earwigs (Forficula auricularia L.), tree crickets (Oecanthus sp.), lacewing larvae (Neuroptera), plant bugs (Miridae), small milkweed bugs (Lygaeus kalmii Stål), ants (Formicidae), spiders (Araneae: Salticidae and other spp.), harvestmen (Opiliones), and velvet mites (Trombidiformes: Trombidiidae). Larvae were attacked by ground beetles (Calleida sp.), jumping spiders (Araneae: Salticidae), and spined soldier bugs (Podisus maculiventris Say). Our findings provide important information about monarch predator–prey interactions that could be used to develop strategies to conserve monarchs through reducing predation on early life stages.

中文翻译：

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视频监控显示一个主要是夜间活动的 Danaus plexippus (L.) 卵食肉动物社区

北美洲东部帝王蝶 (Danaus plexippus L.) 的减少促使非农业草原的马利筋寄主植物恢复工作。然而，草原拥有捕食者群落，对帝王蝶卵和幼虫施加很高的捕食压力。虽然昼伏夜出的帝王捕食者相对众所周知，但没有研究调查过夜间帝王掠食者的贡献。我们使用摄像机监控密歇根州南部乳草上的前哨帝王蝶卵和四龄，以识别捕食者并确定夜间活动的物种是否施加了显着的捕食压力。我们观察到 10 种节肢动物类群消耗帝王蝶卵和幼虫，其中 74% 的卵捕食事件发生在夜间。观察到攻击帝王蝶卵的分类群包括欧洲耳螟（Forficula auricularia L.），蟋蟀 (Oecanthus sp.)、草蛉幼虫 (Neuroptera)、植物臭虫 (Miridae)、小乳草臭虫 (Lygaeus kalmii Stål)、蚂蚁 (Formicidae)、蜘蛛 (Araneae: Salticidae 和其他 spp.)、收割者 (Opiliones)、和绒螨（Trombidiformes：Trombidiidae）。幼虫受到地面甲虫（Calleida sp.）、跳蛛（Araneae：Salticidae）和刺兵虫（Podisus maculiventris Say）的攻击。我们的研究结果提供了关于君主捕食者-猎物相互作用的重要信息，可用于通过减少生命早期阶段的捕食来制定保护君主的策略。幼虫受到地面甲虫（Calleida sp.）、跳蛛（Araneae：Salticidae）和刺兵虫（Podisus maculiventris Say）的攻击。我们的研究结果提供了关于君主捕食者-猎物相互作用的重要信息，可用于通过减少生命早期阶段的捕食来制定保护君主的策略。幼虫受到地面甲虫（Calleida sp.）、跳蛛（Araneae：Salticidae）和刺兵虫（Podisus maculiventris Say）的攻击。我们的研究结果提供了关于君主捕食者-猎物相互作用的重要信息，可用于通过减少生命早期阶段的捕食来制定保护君主的策略。