The orb-weaver spiders Eustala oblonga (Chickering) and Eustala illicita (O. Picard-Cambridge) (Araneae: Araneidae) inhabit the ant-defended acacias Vachellia melanocerus (Beurling) and Vachellia collinsii (Safford) (Fabales: Fabaceae), respectively, in Panama. These spiders do not capture patrolling Pseudomyrmex ants but exploit their plant-protection services to escape predation. What effect the spiders have on the ant-acacia mutualisms is unknown. They may provide an additional layer of plant defense by capturing flying herbivorous insects in their webs. Alternatively, the spiders may disrupt the ant–acacia mutualisms by capturing alate acacia ants during nuptial flights. We evaluated these two hypotheses by sampling insects flying through acacia foliage and by identifying prey remains in webs. The proportions of insects captured on sticky card traps and in webs varied with taxonomic order and ecological role. Herbivorous insects greatly outnumbered other groups captured on sticky cards and were captured in spiders’ webs in both acacia species but made up a minority of prey remains in webs. Instead, insect predators and parasitoids made up the majority of prey remains and were comprised primarily by alate ant mutualists of the host acacias. These results provide indirect support for both hypotheses and suggest that the spiders potentially both benefit and harm their host ant-acacia mutualisms. The net effect of spider exploitation, however, is unclear and is likely based on both the effectiveness of plant protection from herbivory provided by the spiders relative to that provided by acacia ants, as well as the overall proportion of the ant reproductive caste the spiders actually capture.

中文翻译：

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是敌是友？居住在蚂蚁相思树上的宝珠蜘蛛捕获了草食性昆虫和相思蚁。

球形织布蜘蛛Eustala longlonga（Chickering）和Eustala illicita（O. Picard-Cambridge）（Araneae：Araneidae）分别生活在蚂蚁防卫的金合欢（Vachellia melanocerus）（Beurling）和Vachellia Collinsii（Safford）（Fabales：Fabaceae），在巴拿马。这些蜘蛛无法捕获巡逻的Pseudomyrmex蚂蚁，但利用其植物保护服务来逃避捕食。蜘蛛对蚂蚁相思共生有什么影响尚不清楚。它们可以通过在网中捕获飞草食性昆虫来提供额外的植物防御层。另外，蜘蛛可能通过在婚后飞行中捕获迟来的相思树蚂蚁来破坏蚂蚁-相思树的共生关系。我们通过采样穿过相思树叶子的昆虫并确定网中的猎物残留来评估这两个假设。粘性卡陷阱和网中捕获的昆虫比例随分类顺序和生态作用而变化。食草昆虫大大超过了用粘卡捕获的其他种类，并被两种洋槐树种捕获在蜘蛛网中，但只占网中猎物的一小部分。代替，昆虫天敌和寄生类动物构成了大多数猎物的遗骸，主要由寄主相思的晚期蚂蚁互助者组成。这些结果为这两种假设提供了间接支持，并表明蜘蛛潜在地既有利于又损害了其寄主蚂蚁相思的共生关系。但是，对蜘蛛的剥削的净效果尚不清楚，这可能是基于蜘蛛相对于相思类蚂蚁提供的植物对草食的保护作用的有效性以及蜘蛛实际繁殖的蚂蚁种姓的总比例。捕获。