Adult mantis lacewings, neuropteran holometabolan insects of the group Mantispidae, possess anterior walking legs transformed into prey-catching grasping appendages reminiscent of those of praying mantises. While adult mantis lacewings are hence active “wait-and-catch” predators, the larvae of many mantis lacewings have a quite different biology: first-stage larvae seek out female spiders, mount them, and either wait until the spider has produced an egg sac or, in some cases, choose a female already bearing an egg sac. The larva then enters the egg sac and feeds on the eggs. While first stage larvae are highly mobile with comparably long legs and a certain degree of dorso-ventral flattening (“campodeiform”), larval stages two and three are almost immobile, grub-like, and simply remain within the egg sac. Fossils of mantis lacewings are relatively rare, fossils of larval mantis lacewings are even rarer; only a single larva sitting on a juvenile spider has been described from ca. 50 million year old Baltic amber. Here we describe a second occurrence of a larval mantis lacewing from significantly older Burmese amber, about 100 million years old. The specimen is preserved in a position right at the leg of a spider, similar to modern-day larvae that are about to mount their prospective host. The claws of the larva can be seen to grab around the leg of the spider. We discuss how reliable these fossils are as indicators of palaeo-parasitism, and in which aspects the behaviour of mantis lacewing larvae in general indeed represents parasitism. While the specimen appears to be about to board the spider, it may not necessarily represent a parasite in the strict sense. Evaluating the actual ecological role of a fossil heavily depends on comparison to modern forms, and not all modern-day larvae of Mantispidae are parasites. We therefore provide a closer look into the known feeding habits of modern mantis lacewing larvae.

中文翻译：

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寄生虫的旅程：一亿年前的螳螂螳螂幼虫在爬上它的蜘蛛宿主时被捕获

成年螳螂草蛉是螳螂科的神经翅目全变态昆虫，其前足行走变成了捕捉猎物的抓附附属物，让人想起螳螂。虽然成年螳螂草蛉因此是活跃的“等待和捕捉”捕食者，但许多螳螂草蛉的幼虫具有完全不同的生物学：第一阶段的幼虫寻找雌性蜘蛛，登上它们，或者等到蜘蛛产卵囊，或者在某些情况下，选择已经带有卵囊的雌性。然后幼虫进入卵囊并以卵为食。虽然第一阶段的幼虫具有相当长的腿和一定程度的背腹扁平（“campodeiform”）高度移动，但第二和第三阶段的幼虫几乎是不动的，像蛆一样，只是留在卵囊内。螳螂螳螂化石比较少见，螳螂螳螂幼虫化石更罕见；加利福尼亚州仅描述了一只坐在幼蜘蛛上的幼虫。5000 万年历史的波罗的海琥珀。在这里，我们描述了第二次出现的螳螂螳螂幼虫，这种螳螂来自于距今约 1 亿年的非常古老的缅甸琥珀。该标本被保存在蜘蛛腿上的一个位置，类似于即将登上未来宿主的现代幼虫。可以看到幼虫的爪子抓住蜘蛛的腿。我们讨论了这些化石作为古寄生指标的可靠性，以及螳螂草蛉幼虫的行为在哪些方面确实代表了寄生。当标本似乎即将登上蜘蛛时，它可能不一定代表严格意义上的寄生虫。评估化石的实际生态作用在很大程度上取决于与现代形式的比较，并非所有现代螳螂科幼虫都是寄生虫。因此，我们更仔细地研究了现代螳螂草蛉幼虫的已知摄食习性。