蜘蛛位置对成功捕获猎物和球型网图案的影响

静坐在球型网的中心，蜘蛛可能遭受天敌的攻击并暴露在不利的天气条件下，如风和雨。然而，栖居于网的中心使蜘蛛比隐藏在隐蔽场所中的蜘蛛能更迅速地察觉并捕获猎物，这是因为猎物的位置仅能被位于网中心的蜘蛛所确定。对在隐蔽场所中的蜘蛛而言，提高对猎物捕获率的方式之一是尽量减少隐蔽所与网中心的距离。而且，网中心与隐蔽所之间较短的距离使蜘蛛能更迅速地逃离危险境况。我使用既在网中心、又在隐蔽场所的硬类肥蛛(Larinioides sclopetarius Clerck)，来检验这两种行为如何影响对猎物的捕获成功率。隐藏在隐蔽场所中的蜘蛛更经常忽略猎物，使猎物也有比较多的逃离机会，这样，与在网中心的蜘蛛相比，猎物的损失率就更高。另外，研究了隐蔽场所的位置对球型网图案的影响。在大多数球型网中，网中心上方的区域比网下方小，丝也比较少，形成了结构不对称的网；隐蔽场所通常在网的上方。当隐蔽场所的位置在实验中被倒转时，就形成了非典型的球型网。最后，L．sclopetarius建造的网有很突出的边缘非对称性，与隐蔽场所相邻的区域面积较小，而远离隐蔽场所的区域面积较大，这也可解释为减少了隐蔽场所和网中心之间的距离动物学报50(4)：559-565．2004]。

Effect of spider position on prey capture success and orb-web design

Sitting in the hub of an orb web,spiders may suffer from exposure to predators and unfavourable weather conditions such as wind and rain.However,residing at the hub allows spiders to detect and capture prey more quickly than spiders hidden in a retreat,because prey can only be localised by the spider positioned in the hub of the web.One way of reducing the costs of delayed prey capture is to keep the distance between retreat and hub as short as possible.Furthermore,a shorter hub retreat distance allows spiders to escape dangerous situations more rapidly.I used female bridge spider Larinioides sclopetarius Clerck(Araneae:Araneidae),a nocturnal orb web spider that is either found in the hub or in the retreat,to test how these two behaviours influence prey capture success.Spiders hidden in the retreat more frequently ignored prey which also had a higher chance of escape,resulting in a higher rate of prey loss compared to spiders residing in the hub.Additionally,the influence of retreat position on web design was investigated.In most orb webs the region above the hub is smaller and contains less silk than the region below the hub,creating an asymmetrical web;the retreat is usually located above the web.When the position of the retreat was experimentally reversed,less material covering a smaller area was used for the region below the hub and closer to the retreat compared to the region above,creating an atypical orb web.Finally,the webs constructed by L sclopetarius showed a pronounced lateral asymmetry with a reduced region adjacent to the retreat and an enlarged region away from the retreat,which also translated into a reduced retreat hub distance