Knowledge of the life‐history traits that influence the reproductive success of parasitoids could provide useful information to enhance their effectiveness as biological control agents. The wheat stem sawfly Cephus cinctus Norton (Hymenoptera: Cephidae) is a major pest of wheat in the Northern Great Plains of North America. The bivoltine, sympatric and specialist parasitoids Bracon cephi (Gahan) and Bracon lissogaster Muesebeck (Hymenoptera: Braconidae) are the only species known to attack C. cinctus in wheat. In the present study, we quantify the body size, longevity, egg load and egg volume of B. cephi and B. lissogaster aiming to test whether these life‐history traits differ among adult females developing from overwintering and summer generation larvae. We also investigate the effect of sucrose supplementation on the same reproductive parameters. The results obtained show no differences between life‐history traits of B. cephi developing from the overwintering and summer generations. By contrast, the egg load of B. lissogaster is significantly different between generations, with overwintered females producing 1.2‐fold more eggs than summer individuals. Sucrose feeding has a strong positive effect on life‐history traits of both parasitoid species and generations. The longevity of sucrose‐fed females of B. cephi is increased three‐fold, whereas the survival of B. lissogaster is increased almost nine‐fold. Females of B. cephi treated with sucrose have four‐fold more mature eggs, whereas the egg load of B. lissogaster is increased 1.15‐ to 1.25‐fold with sugar feeding. Only B. cephi females increase egg volume with sucrose. The present study provides valuable insights on the life‐history and nutritional requirements of these two important parasitoid species.

中文翻译：

---

蔗糖补充和生成对小麦茎叶蜂寄生蜂Bracon cephi和Bracon lissogaster生活史性状的影响

了解影响寄生物繁殖成功的生活史特征可以提供有用的信息，以提高它们作为生物防治剂的有效性。小麦茎叶蜂Cephus cinctus Norton（膜翅目：Cephidae）是北美大平原北部小麦的主要害虫。bivoltine、同域和专业寄生蜂Bracon cephi (Gahan) 和Bracon lissogaster Muesebeck (膜翅目： Braconidae) 是已知的唯一攻击小麦中的C. cinctus 的物种。在本研究中，我们量化了头孢双歧杆菌和 B. lissogaster 的体型、寿命、产卵量和卵体积，旨在测试这些生活史特征在从越冬和夏季一代幼虫发育的成年雌性中是否存在差异。我们还研究了蔗糖补充对相同繁殖参数的影响。所得结果表明，从越冬世代和夏季世代发展而来的 B. cephi 的生活史特征没有差异。相比之下，B. lissogaster 的产卵量在各代之间存在显着差异，越冬雌性产卵量是夏季个体的 1.2 倍。蔗糖喂养对寄生蜂物种和世代的生活史特征有很强的积极影响。B. cephi 的蔗糖喂养雌性的寿命增加了三倍，而 B. lissogaster 的存活率增加了近九倍。B. cephi 雌性用蔗糖处理的成熟卵增加了四倍，而 B. lissogaster 的卵负荷增加了 1.15 到 1.25 倍，用糖喂养。只有 B。cephi 雌性用蔗糖增加卵体积。本研究为这两种重要寄生蜂的生活史和营养需求提供了宝贵的见解。