The quality of hosts for a parasitoid wasp may be influenced by attributes such as host size or species, with high quality for successful development usually coincident with high quality for larger offspring. This is not always the case: for the Scelionid wasp Trissolcus basalis, oviposition in eggs of the Brown Marmorated Stink Bug, Halyomorpha halys, rather than of the normal host, the Southern Green Stink Bug, Nezara viridula, leads to lower offspring survival, but survivors can be unusually large. Adult female T. basalis engage in contests for host access. As larger contestants are typically favoured in contests between parasitoids, the larger size of surviving offspring may compensate for the mortality of others. We construct a general game-theoretic model to explore whether size advantage can sustain a maternal preference to utilize a more deadly host species. We find that size advantage alone is unlikely to sustain a shift in host preference, yet such an outcome is possible when size asymmetries act simultaneously with advantages in host possession (ownership effect). Halyomorpha halys is an invasive pest of major agro-economic importance in Europe and the Americas, and use of its eggs as hosts by native parasitoids such as T. basalis has been seen as an evolutionary trap due to their high developmental mortality. Our model suggests that the recently discovered effect of host choice on offspring size may provide an escape from the trap via effects on contest biology of T. basalis which could foster a more stable association with H. halys. An evolutionary shift in the reproductive value of H. halys could increase the efficiency of T. basalis as a biological control agent of this invasive stink bug pest.

寄生蜂的寄主质量可能受寄主大小或物种等属性的影响，成功发育的高质量通常与较大后代的高质量一致。情况并非总是如此：对于 Scelionid 黄蜂Trissolcus basalis 而言，在棕色 Marmorated Stink Bug Halyomorpha halys 的卵中产卵，而不是正常宿主南方绿色 Stink Bug Nezara viridula 的卵产卵，导致后代存活率降低，但是幸存者可能异常大。成年雌性T. basalis参加主机访问竞赛。由于较大的竞争者通常在寄生蜂之间的竞争中受到青睐，因此较大的存活后代可能会弥补其他人的死亡。我们构建了一个通用的博弈论模型来探索体型优势是否可以维持母体偏好使用更致命的宿主物种。我们发现仅靠体型优势不太可能维持宿主偏好的转变，但当体型不对称与宿主占有优势（所有权效应）同时作用时，这种结果是可能的。Halyomorpha halys是一种在欧洲和美洲具有重要农业经济重要性的入侵性害虫，其卵被本地寄生蜂如T. basalis用作寄主由于它们的高发育死亡率，已被视为进化陷阱。我们的模型表明，最近发现的宿主选择对后代大小的影响可能会通过对T. basalis竞争生物学的影响来摆脱陷阱，这可能会促进与H. halys的更稳定的关联。H. halys繁殖价值的进化转变可以提高T. basalis作为这种入侵性臭虫害虫的生物防治剂的效率。