Ecdysteroids are a family of insect hormones that may play a role in modulating aggressive behavior in reproductive contexts. In Hymenoptera, the few studies investigating the link between ecdysteroid titers, reproduction and aggressiveness during contests concern solely eusocial species. Here, we explored whether ecdysteroid titers influenced female reproductive status as well as aggressiveness and resolution of conflict in a solitary ectoparasitoid, Eupelmus vuilleti (Hymenoptera: Eupelmidae). Eupelmus vuilleti females parasitize and feed upon juvenile stages of Callosobruchus maculatus (Coleoptera: Bruchidae). When two E. vuilleti females are simultaneously present on a patch, they tend to protect the host they exploit by displaying aggressive behaviors towards conspecific competitors. To our knowledge, nothing is known about the association between ecdysteroids and aggressiveness or the outcome of contests for host access in solitary insects. First, we quantified ecdysteroid titers that naturally circulate in females without fighting experience and after a contest over host access. Ecdysteroid titers measured after the contest did not correlate with female aggressiveness during the contest, but winner wasps had higher titers than both losers and females that did not fight. Then, we manipulated hormone titers via injection: ecdysone favored egg maturation (i.e., gonadotropic effect) within 24 h and increased almost immediately the females' probability of winning host access without affecting their aggressiveness. Our results represent an important step in understanding how hormones, such as ecdysteroids, mediate insect behavior during intraspecific competition.

蜕皮类固醇是昆虫激素家族，可能在调节生殖环境中的侵略性行为中发挥作用。在膜翅目中，很少有研究调查比赛中蜕皮甾类滴度，繁殖与攻击性之间的联系的研究仅涉及真社会物种。在这里，我们探讨了蜕皮类固醇滴度是否会影响女性生殖状态以及在孤立的类外寄生物Eupelmus vuilleti（膜翅目：Eupelmidae）中的侵略性和解决冲突的能力。Eupelmus vuilleti雌性寄生于斑os（Callosobruchus maculatus）的幼年期，并以其为食。当两个E. vuilleti雌性同时出现在斑块上，它们倾向于通过对同种竞争者表现出攻击性行为来保护所利用的宿主。据我们所知，关于蜕皮类固醇与侵略性之间的联系或孤立昆虫中宿主进入比赛的结果一无所知。首先，我们对蜕皮类固醇滴度进行了定量，这些蜕皮类固醇滴度在雌性中自然传播，而没有战斗经验，并且在争夺宿主的比赛之后。比赛后测得的蜕皮甾体滴度与比赛中的女性侵略性无关，但胜者黄蜂的滴度要高于失败者和未战斗的雌性。然后，我们通过注射来控制激素滴度：蜕皮激素有利于24小时内卵成熟（即促性腺激素作用），几乎立即增加了雌性 在不影响主机侵略性的情况下赢得主机访问权的可能性。我们的结果代表了了解激素（如蜕皮类固醇）如何在种内竞争过程中介导昆虫行为的重要一步。