Termites are “social cockroaches” and amongst the most phenotypically plastic insects. The different castes (i.e., two types of reproductives, workers, and soldiers) within termite societies are all encoded by a single genome and present the result of differential postembryonic development. Besides the default progressive development into winged sexuals of solitary hemimetabolous insects, termites have two postembryonic, non-terminal molts (stationary and regressive; i.e., molts associated, respectively, with no change or reduction of size/morphological differentiation) which allow them to retain workers, and two terminal developmental types to become soldiers and replacement reproductives. Despite this unique plasticity, especially the mechanisms underlying the non-terminal development are poorly understood. In 1982, Nijhout and Wheeler proposed a model how this diversity might have evolved. They proposed that varying juvenile hormone (JH) titers at the start, mid-phase, and end of each intermolt period account for the developmental diversity. We tested this rarely addressed model in the lower termite Cryptotermes secundus using phase-specific pharmacological manipulations of JH titers. Our results partially support the Nijhout and Wheeler model. These data are supplemented with gene expression studies of JH-related genes that characterize different postembryonic developmental trajectories. Our study provides new insights into the evolution of the unique postembryonic developmental plasticity of termites that constitutes the foundation of their social life.

白蚁是“社会蟑螂”，也是最表型可塑性的昆虫之一。白蚁社会中不同的种姓（即，两种类型的生殖，工人和士兵）全都由单一基因组编码，并呈现出不同的胚后发育结果。除了默认的渐进性发展为孤立的半代谢昆虫的有翅性昆虫之外，白蚁还具有两个胚后的非末端（固定的和回归的mol，分别是相关的，没有改变或减小大小/形态的分化），从而使它们得以保留。工人和两种终端发展型成为士兵和替代性生殖。尽管具有这种独特的可塑性，但对非末端发育的潜在机制尤其知之甚少。1982年，Nijhout和Wheeler提出了一个模型，说明这种多样性可能是如何演变的。他们提出，在每个蜕皮期的开始，中期和结束时，幼体激素（JH）效价的变化都说明了发育的多样性。我们在下白蚁中测试了这个很少解决的模型隐孢子虫使用JH效价的阶段特定药理学操作。我们的结果部分支持了Nijhout和Wheeler模型。这些数据补充了JH相关基因的基因表达研究，这些研究表征了不同的胚胎后发育轨迹。我们的研究为白蚁独特的胚胎后发育可塑性的演变提供了新见解，白蚁是构成其社会生活的基础。