Many parasitoid species discriminate already parasitized hosts, thus avoiding larval competition. However, females incur in superparasitism under certain circumstances. Superparasitism is commonly observed in the artificial rearing of the parasitoid Diachasmimorpha longicaudata, yet host discrimination has been previously suggested in this species. Here, we addressed host discrimination in virgin D. longicaudata females in a comprehensive way by means of direct and indirect methods, using Ceratitis capitata and Anastrepha fraterculus which are major fruit fly pests in South America. Direct methods relied on the description of the foraging behaviour of females in arenas with parasitized and non-parasitized host larvae. In the indirect methods, healthy larvae were offered to single females and the egg distributions were compared to a random distribution. We found that D. longicaudata was able to recognize parasitized host from both host species, taking 24 h since a first parasitization for A. fraterculus and 48 h for C. capitata. Indirect methods showed females with different behaviours for both host species: complete discrimination, non-random (with superparasitism), and random distributions. A larger percentage of females reared and tested on A. fraterculus incurred in superparasitism, probably associated with higher fecundity. In sum, we found strong evidence of host discrimination in D. longicaudata, detecting behavioural variability associated with the host species, the time since the first parasitization and the fecundity of the females.

中文翻译：

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果蝇寄生蜂 Diachasmimorpha longicaudata 的宿主歧视：来自处女雌性行为和卵分布模式的证据

许多寄生蜂物种区分已经寄生的宿主，从而避免幼虫竞争。然而，在某些情况下，雌性会产生超寄生。超寄生现象在寄生蜂的人工饲养中很常见长尾石竹，但以前曾在该物种中提出过宿主歧视。在这里，我们解决了处女的主机歧视问题D. longicaudata通过直接和间接的方法，综合运用女性头孢菌素和实蝇是南美洲主要的果蝇害虫。直接方法依赖于对寄生和非寄生宿主幼虫在竞技场中雌性觅食行为的描述。在间接方法中，将健康的幼虫提供给单身雌性，并将卵分布与随机分布进行比较。我们发现D. longicaudata能够识别来自两种宿主物种的寄生宿主，自第一次寄生以来需要 24 小时A. fraterculus和 48 小时C.capita. 间接方法显示雌性对两种宿主物种具有不同的行为：完全歧视、非随机（具有超寄生性）和随机分布。更大比例的雌性被饲养和测试A. fraterculus在超寄生中发生，可能与更高的繁殖力有关。总之，我们发现了宿主歧视的有力证据D. longicaudata，检测与宿主物种相关的行为变异性，自第一次寄生以来的时间和雌性的繁殖力。