The number of conspecifics present during the juvenile stages can have profound consequences on development rates and adult body size, traits often closely related to fitness. Conspecifics can have direct negative effects on each other due to resource competition, and also direct positive effects due to benefits like improved thermoregulation. We investigated morphological and developmental consequences of juvenile group size in the leaf-footed cactus bug Narnia femorata (Hemiptera: Coreidae). These insects are ideal to test the consequences of social environment during development because nymphs naturally aggregate in groups of varying size. Furthermore, the sexual dimorphism of this species allowed us to test for sex-specific effects of developmental density. Males possess enlarged hind legs used as weapons in male-male contests, yet females are physically larger. We found insects from smaller groups had 43% higher mortality than those from the larger groups. On average, adult body and hind leg sizes did not differ across densities for either sex. Interestingly, we found that those first to mature into adults within a sibling group became the largest adults. The largest, fastest males to adulthood also wielded the biggest weapons due to the positive allometry of this trait.

中文翻译：

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在两性性物种中聚集幼体的群体生活的隐性成本

幼年阶段存在的同种异形体的数量可能对发育速度和成年体重产生深远影响，这些特征通常与适应性密切相关。由于资源竞争，同种异构体可能对彼此产生直接的负面影响，而由于改善的温度调节等优点，同种物质也可能产生直接的正面影响。我们调查了叶足仙人掌臭虫纳尼亚尼亚仙女幼体大小的形态和发育后果（半翅目：Core科）。由于若虫自然会以不同大小的群体聚集，因此这些昆虫是测试发育过程中社会环境后果的理想选择。此外，该物种的性二态性使我们能够测试发育密度的性别特异性影响。雄性拥有扩大的后腿，在男女竞赛中用作武器，而雌性则身体更大。我们发现，小群昆虫的死亡率比大群昆虫高43％。平均而言，两种性别的成年人的身体大小和后腿的大小都没有差异。有趣的是，我们发现那些最早在同胞组中长大成人的人成为最大的成年人。成年男性中最大，最快的男性也拥有最大的武器，这是因为该特征具有正向异性。