（图片来源于网络）

根据任何物理学法则，像狼蛛这样又大又重的蜘蛛都是不能爬墙或倒挂的——它们应当会一头栽到地上。

然而尽管有点费劲，但狼蛛却能够攀爬，于是研究人员决定找出问题的答案。

他们采集了几种狼蛛蜕掉的外皮，其中就包括第一作者本人挚爱的刚刚离世的宠物——毛球（如上图）。研究人员发现，狼蛛毛茸茸的脚底覆盖着细微的毛发，其作用相当于一根黏丝的“阀门”，它们只有在狼蛛开始坠落时才被打开。

由于大多数蜘蛛都会从腹部的吐丝器中制造蛛丝，因此这一发现可能有助于解释蜘蛛是如何将它们的蛛丝进化出这么多的用途的。

研究人员在6月份出版的《实验生物学期刊》上报告了这一研究成果。这还解释了为什么狼蛛走过的地方总会留下少量丝制的脚印。

原文：

The Journal of Experimental Biology      DOI: 10.1242/?jeb.055657

Tarantulas cling to smooth vertical surfaces by secreting silk from their feet

F. Claire Rind, Chris Luke Birkett, Benjamin-James A. Duncan1 and Alexander J. Ranken

Like all spiders, tarantulas (family Theraphosidae) synthesize silk in specialized glands and extrude it from spinnerets on their abdomen. In one species of large tarantula, Aphonopelma seemanni, it has been suggested that silk can also be secreted from the tarsi but this claim was later refuted. We provide evidence of silk secretion directly from spigots (nozzles) on the tarsi of three distantly related tarantula species: the Chilean rose, Grammostola rosea; the Indian ornamental, Poecilotheria regalis; and the Mexican flame knee, Brachypelma auratum, suggesting tarsal silk secretion is widespread among tarantulas. We demonstrate that multiple strands of silk are produced as a footprint when the spider begins to slip down a smooth vertical surface. The nozzle-like setae on the tarsi responsible for silk deposition have shanks reinforced by cuticular thickenings, which serve to prevent the shanks' internal collapse while still maintaining their flexibility. This is important as the spigots occur on the ventral surface of the tarsus, projecting beyond the finely divided setae of the dry attachment pads. We also reveal the structure and disposition of the silk-secreting spigots on the abdominal spinnerets of the three tarantula species and find they are very similar to those from the earliest known proto-spider spinneret from the Devonian period, giving another indication that silk secretion in tarantulas is close to the ancestral condition.