Department of Zoology, University of Florida, 32611, Gainesville, FL.
J Chem Ecol. 1983 Apr;9(4):521-32. doi: 10.1007/BF00990224.
Cycnia tenera adults, reared as larvae onAsclepias humistrata, had 10 times higher cardenolide concentrations, and contained 15 times more total cardenolide, than did moths reared onA. tuberosa. Thin-layer chromatography confirmed that each individual cardenolide visualized in the adult moths reared on the former host plant corresponds to one present in the plant, thus demonstrating that the insects' cardenolides are indeed derived from the larval food. Adult weights were significantly greater when the larvae had been fed upon the higher cardenolide plant species,A. humistrata. Similar results for other milkweed-feeding insects have been interpreted by some authors as evidence against a metabolic cost of handling cardenolides. However, such interpretations confound cardenolide differences among milkweed species with other differences in plant primary and secondary chemistry that affect insect growth and development. While the cooccurrence inC. tenera of other noxious chemicals (e.g., alkaloids) is not precluded, cardenolides sequestered from larval host plants have probably contributed to the evolution of visual and auditory aposematism in this species. As the eggs are laid in large clutches and larvae are gregarious, such aposematism may have evolved via kin selection.
柔弱云实成蛹，幼虫以马利筋为食，体内的强心甾配糖体浓度比以乳草为食的成蛾高 10 倍，总强心甾配糖体含量高 15 倍。薄层层析证实，前一种宿主植物上饲养的成蛾中每种个体可见的强心甾配糖体，都与植物中的一种相对应，从而表明昆虫的强心甾配糖体确实来源于幼虫的食物。当幼虫以含有较高强心甾配糖体的植物柔弱云实为食时，成蛾的体重显著增加。一些作者将其他以乳草为食的昆虫的类似结果解释为代谢处理强心甾配糖体无成本的证据。然而，这种解释将乳草物种间的强心甾配糖体差异与影响昆虫生长和发育的植物初级和次级化学成分的其他差异混淆在一起。虽然不能排除柔弱云实中存在其他有毒化学物质（如生物碱）的共同存在，但从幼虫宿主植物中摄取的强心甾配糖体可能有助于该物种视觉和听觉警戒的进化。由于卵大量产下，且幼虫群居，这种警戒可能是通过亲缘选择进化而来的。
