DISSERTATION RESEARCH: Costs and Benefits of Shelter-Building by Lepidopteran Caterpillars in a Tropical Dry Forest

成千上万种毛毛虫用蚕丝和树叶筑巢。其中许多种类丰富，是重要的森林害虫。然而，人们对庇护所如何影响毛毛虫的生存以及最终成年后的产卵量知之甚少。该项目将提供有关庇护所对毛毛虫生存和成虫成功的影响的信息。首先，该项目测试了庇护所在高温和低湿条件下提供的保护程度。这些信息将有助于确定毛毛虫对环境的敏感程度，阐明当地和全球气候的变化如何影响建造庇护所的物种的成功。其次，该项目将测试庇护所对掠食性昆虫和蜘蛛、寄生蜂和苍蝇的保护作用。具体来说，这些实验将确定毛毛虫的庇护所是否能更好地保护它们免受捕食者的侵害，它们是否更容易受到寄生昆虫的伤害。捕食者和寄生昆虫都被用来控制害虫，因此测试这一假设可以应用于害虫管理。由于研究地点在哥斯达黎加，这组科学家还将提高对一个未被充分研究的热带栖息地（热带干燥森林）的认识，并促进国际联系和培训。研究人员将进行两组实验，使用合作建造群体庇护所的毛毛虫物种，在那里可以发现两到十只毛毛虫住在一起。两组实验都将在毛虫的自然森林栖息地进行。第一个实验将测量庇护所和环境对四种毛毛虫生存的影响。毛毛虫以及温度和湿度传感器将被放置在毛毛虫的庇护所内外。将监测毛毛虫的生存情况，以确定毛毛虫是否被它们的庇护所保护起来，不受外界环境的影响。第二个实验将衡量为两种毛毛虫建造和共享群体庇护所的成本和收益。毛毛虫将被允许单独或成群地建造庇护所，并将测量由捕食者和寄生昆虫造成的死亡率。如果一些治疗方法不太可能被捕食者杀死，研究人员将测试毛毛虫是否也更有可能被寄生昆虫攻击。与其他毛毛虫共用一个庇护所的积极和消极影响也将通过称重幸存的毛毛虫的蛹来衡量。较重的蛹通常会成为产生更多后代的成年人，因此这项措施将使研究人员能够确定共享一个避难所是有负面影响（由于与其他毛毛虫竞争）还是有积极影响（由于分担建造和维护避难所的成本）。

Tens of thousands of caterpillar species build shelters out of silk and leaves. Many are sufficiently abundant that they are important forest pests. However, little is known about how shelters affect the survival of the caterpillars and ultimately their egg production as adults. This project will provide information on the impact that shelters have on caterpillar survival and adult success. First, the project tests how much protection shelters provide from high temperatures and low humidity. This information will help determine how sensitive the caterpillars are to their environment, clarifying how changes in local and global climate might influence the success of shelter-building species. Second, the project will test the protective effects of shelters against predatory insects and spiders, and against parasitic wasps and flies. Specifically, the experiments will determine whether caterpillars whose shelters provide better protection against predators are more vulnerable to parasitic insects. Both predators and parasitic insects are used to control pest insects, so testing this hypothesis could be applied to pest management. Because the research site is in Costa Rica, the researchers will also increase awareness of an under-studied tropical habitat (tropical dry forests) and foster international connections and training.The researchers will perform two sets of experiments using caterpillar species that cooperatively build group shelters, in which two to ten caterpillars can be found living together. Both sets of experiments will be conducted in the natural forest habitat of the caterpillars. The first experiment will measure the effects of shelters and the environment on caterpillar survival for four species. Caterpillars, along with temperature and humidity sensors, will be placed both inside and outside caterpillar shelters. Caterpillar survival will be monitored to determine whether the caterpillars are protected from the outside environment by their shelters. The second experiment will measure the costs and benefits of building and sharing group shelters for two caterpillar species. Caterpillars will be allowed to build shelters either alone or in groups, and the mortality caused by predators and parasitic insects will be measured. If some treatments are less likely to be killed by predators, the researchers will test whether the caterpillars are also more likely to be attacked by parasitic insects. The positive and negative effects of sharing a shelter with other caterpillars will also be measured by weighing the pupae of surviving caterpillars. Heavier pupae become adults who generally produce more offspring, so this measure will allow the researchers to determine whether sharing a shelter has a negative effect (due to competition with other caterpillars) or a positive one (due to sharing the costs of building and maintaining the shelter).