Data from: Ontogenetic changes in the body temperature of an insect herbivore

1. Over ontogeny, many insect larvae grow substantially, through at least several orders of magnitude in body size. Increasing size can profoundly change how individuals interact with their environments, by altering the opportunities for, and constraints on, feeding, changing the relative risk and sources of predation, and shifting the relative importance of physical factors in the environment. 2. Here I use eggs and larvae of Manduca sexta, which are herbivores on solanaceous plants in the southwestern US, to examine how body size affects body temperature. Larvae grow in excess of 10,000-fold by mass in a few weeks, from 0.001-g hatchlings to 12 – 15-g 5th-instar larvae. 3. Using infrared thermography, I show that increasing body size leads to large changes in body temperature: over ontogeny, average larval temperature increased by 3 – 7°C. The temperatures of eggs, hatchlings, and early larval instars were coupled to leaf temperatures (Datura wrightii), which were much cooler than ambient air temperatures. The temperatures of larger larvae, by contrast, were similar to air temperatures, or somewhat higher. 4. Changing body temperatures reflect that small and large larvae were immersed differentially in leaf boundary layers, received different amounts of incoming solar radiation, and used thermal heterogeneity on leaf surfaces in different ways. 5. I develop a simple species distribution model that links maximum observed air temperatures in the southwestern US with known thermal tolerances of eggs and larvae. This model predicts that eggs of M. sexta can occupy significantly larger fractions of the landscape than can large larvae. 6. Large differences among stage-specific microclimates, such as those observed for M. sexta, are likely to be general features for insects and other organisms whose body sizes span large ranges, and stage-specific microclimates pose general and largely unrecognized problems for species distribution models.1. 在个体发育（ontogeny）过程中，多数昆虫幼虫会发生显著生长，体型大小增幅可达至少数个数量级。体型增大可从多方面深刻改变个体与环境的互作模式：改变取食的机会与限制条件、改变捕食风险的相对程度与捕食来源、以及改变环境中物理因素的相对重要性。2. 本研究以分布于美国西南部、取食茄科（solanaceous）植物的植食性昆虫烟草天蛾（Manduca sexta）的卵和幼虫为研究对象，探究体型大小对体温的影响。该物种幼虫在数周内的体质量增幅可超过10000倍，从初孵幼虫的0.001克生长至5龄幼虫的12至15克。3. 本研究借助红外热成像技术（infrared thermography）发现，体型增大可导致体温发生显著变化：在个体发育过程中，幼虫的平均体温可升高3至7摄氏度。卵、初孵幼虫以及早期龄期幼虫的体温与莱特曼陀罗（Datura wrightii）叶片温度保持同步，而叶片温度远低于环境空气温度。与之相反，体型较大的幼虫体温与空气温度相近，甚至略高于空气温度。4. 体温的变化差异源于小型与大型幼虫所处的叶片边界层条件存在显著差异、接收的入射太阳辐射量不同，以及对叶片表面热异质性的利用模式存在差异。5. 本研究构建了一个简单的物种分布模型（species distribution model），该模型将美国西南部实测的最高气温与卵和幼虫已知的耐热性进行关联。模型预测，烟草天蛾的卵可占据的生境面积比例显著高于大型幼虫。6. 像烟草天蛾这类存在显著阶段特异性微气候差异的类群，其特征很可能广泛存在于体型跨度较大的昆虫及其他生物类群中；而阶段特异性微气候则为物种分布模型带来了普遍且大多未被学界认知的问题。