Trophic-egg producing strategies in subsocial cydnid bugs

营养卵是不能存活的，通常作为后代的食物供应，一直被认为是父母延长投资或兄弟姐妹食卵中亲子冲突的结果。三角叶蝉和日本副星虫是一种亚社会昆虫，表现出一种复杂的母性照顾模式，包括防御捕食者、逐步提供寄主果实和产生营养卵。为了研究营养卵的功能，我们通过实验将营养卵从窝中取出，并比较了有营养卵的若虫和没有营养卵的若虫的性能，包括活卵食人的发生率。摄食营养卵能提高三叉戟和日本对虾后代的存活和/或发育。在三叶蜂中，一些可存活的卵也以兄弟若虫为食。然而，在有和没有营养卵的情况下，幼崽消耗的可存活卵的比例没有差异。雌体大小影响其对营养卵的相对投资：体型较大的雌体产卵较多，而营养卵相对较少。为了研究雌体所经历的食物资源环境对营养卵产量的影响，我们在产卵前的不同资源条件下饲养了雌虫，并比较了随后营养卵的分配情况。提供不发达种子的雌性比提供发育良好种子的雌性产生更少的可存活卵。根据上述两个假设和资源环境的适应性母体效应，讨论了营养卵子的功能和适应性分配

Trophic eggs, which are inviable and usually function as a food supply for offspring, have been regarded as extended parental investment or the outcome of parent-offspring conflict in sibling oophagy. Adomerus triguttulus and Parastrachia japonensis (Heteroptera : Cydnidae) are subsocial bugs showing a complex pattern of maternal care, including defense against predators, progressive provisioning of host fruit and trophic-egg production.To investigate the functions of trophic eggs, we conducted experimental removal of trophic eggs from clutches and compared performance, including the incidence of viable-egg cannibalism, of nymphs with trophic eggs and those without trophic eggs. Trophic-egg feeding enhances offspring survival and/or development in A. triguttulus and P.japonensis. In A.triguttulus, some viable eggs were also fed upon by sibling nymphs. However, there was no difference in the proportion of viable eggs consumed between clutches with and without trophic eggs. The body size of A.triguttulus females affected their relative investment in trophic eggs : larger females produced more viable eggs with relatively fewer trophic eggs.To investigate the effects of food-resource environments that A.triguttulus females experience on trophic-egg production, we reared females under different resource conditions prior to oviposition and then compared the subsequent allocations of trophic eggs. Females that had been supplied with less-developed seeds produced fewer viable eggs than those supplied with well-developed seeds. However, there was no difference in the number of trophic eggs between them, and thus the number of trophic eggs per viable egg was higher in females supplied with less-developed seeds.The functions and adaptive allocation of trophic eggs are discussed in light of the two hypotheses mentioned above and the adaptive maternal effects under fluctuating resource environments