Many insects feed on a low‐nitrogen diet, and the origin of their nitrogen supply is poorly understood. It has been hypothesized that some insects rely on nitrogen‐fixing bacteria (diazotrophs) to supplement their diets. Nitrogen fixation by diazotrophs has been extensively studied and convincingly demonstrated in termites, while evidence for the occurrence and role of nitrogen fixation in the diet of other insects is less conclusive. Here, we summarize the methods to detect nitrogen fixation in insects and review the available evidence for its occurrence (focusing on insects other than termites). We distinguish between three aspects of nitrogen fixation investigations: (i) detecting the presence of potential diazotrophs; (ii) detecting the activity of the nitrogen‐fixing enzyme; and (iii) detecting the assimilation of fixed nitrogen into the insect tissues. We show that although evidence from investigations of the first aspect reveals ample opportunities for interactions with potential diazotrophs in a variety of insects, demonstrations of actual biological nitrogen fixation and the assimilation of fixed nitrogen are restricted to very few insect groups, including wood‐feeding beetles, fruit flies, leafcutter ants, and a wood wasp. We then discuss potential implications for the insect's fitness and for the ecosystem as a whole. We suggest that combining these multiple approaches is crucial for the study of nitrogen fixation in insects, and argue that further demonstrations are desperately needed in order to determine the relative importance of diazotrophs for insect diet and fitness, as well as to evaluate their overall impact on the ecosystem.

中文翻译：

---

我们对昆虫的生物固氮了解多少？昆虫和生态系统的证据和影响

许多昆虫以低氮饮食为食，对其氮供应的来源知之甚少。据推测，一些昆虫依靠固氮细菌（固氮菌）来补充它们的饮食。固氮菌的固氮作用已在白蚁中得到广泛研究并得到令人信服的证明，而关于固氮在其他昆虫饮食中的发生和作用的证据则不太确定。在这里，我们总结了检测昆虫固氮的方法并回顾了其发生的可用证据（重点是除白蚁以外的昆虫）。我们区分固氮研究的三个方面：(i) 检测潜在固氮菌的存在；(ii) 检测固氮酶的活性；(iii) 检测固定氮对昆虫组织的同化。我们表明，虽然第一方面的调查证据揭示了与各种昆虫中潜在固氮菌相互作用的充足机会，但实际生物固氮和固氮同化的示范仅限于极少数昆虫群，包括食木甲虫、果蝇、切叶蚁和木蜂。然后，我们讨论对昆虫的适应性和整个生态系统的潜在影响。我们建议将这些多种方法结合起来对于研究昆虫的固氮至关重要，并认为迫切需要进一步的论证来确定固氮菌对昆虫饮食和健康的相对重要性，