Body size is an important phenotypic trait that correlates with performance and fitness. For determinate growing insects, body size variation is determined by growth rate and the mechanisms that stop growth at the end of juvenile growth. Endocrine mechanisms regulate growth cessation, and their relative timing along development shapes phenotypic variation in body size and development time. Larval insects are generally hypothesized to initiate metamorphosis once they attain a critical weight. However, the mechanisms underlying the critical weight have not been resolved even for well-studied insect species. More importantly, critical weights may or may not be generalizable across species. In this study, we characterized the developmental aspects of size regulation in the solitary bee, Osmia lignaria. We demonstrate that starvation cues metamorphosis in O. lignaria and that a critical weight does not exist in this species. Larvae initiated pupation <24 h after food was absent. However, even larvae fed ad libitum eventually underwent metamorphosis, suggesting that some secondary mechanism regulates metamorphosis when provisions are not completely consumed. We show that metamorphosis could be induced by precocene treatment in the presence of food, which suggests that this decision is regulated through juvenile hormone signaling. Removing food at different larval masses produced a 10-fold difference in mass between smallest and largest adults. We discuss the implications of body size variation for insect species that are provided with a fixed quantity of provisions, including many bees which have economic value as pollinators.

中文翻译：

---

食物的缺乏而不是孤蜂Osmia lignaria的临界体重导致了变态

体型是一项重要的表型特征，与表现和健康状况相关。对于确定的正在生长的昆虫，其体型大小的变化取决于生长速率以及在幼虫生长结束时停止生长的机制。内分泌机制调节生长停止，并且它们沿发育的相对时间塑造了体型和发育时间的表型变化。一般认为，幼虫一旦达到临界体重，便会开始变态。然而，即使对于经过充分研究的昆虫物种，临界重量的潜在机制仍未得到解决。更重要的是，关键权重可能会或可能不会在整个物种中推广。在这项研究中，我们描述了单蜂Osmia lignaria中大小调节的发展方面。。我们证明饥饿提示在O. lignaria中发生了变态并且该物种中不存在临界重量。食物不足后的24小时内，幼虫开始化脓。但是，即使随意喂食幼虫，最终也会发生变态，这表明某些准备工作没有完全消耗掉时，次级机制就可以调节变态。我们表明，变态可以通过在食物的存在下进行的并新世治疗来诱导，这表明该决定是通过幼体激素信号传导来调节的。除去不同幼虫质量的食物，在最小和最大的成年动物之间产生了10倍的质量差异。我们讨论了体型变化对具有固定数量规定的昆虫物种的影响，其中包括许多具有授粉媒介经济价值的蜜蜂。