Form and Functions

 The Cyclosa conica is able to move like any other spider, it moves by using a system called hydraulics.  Hydraulics is defined as a process in which power is generated and transmitted by use of pressurized liquids (Pomeroy).  Other arthropods have extensor muscles located in their major leg joints, but the Cyclosa conica and other spiders don’t have these extensor muscles.  Cyclosa conica are able to extend their hind legs for movement by using hydraulic pressure that is generated in the prosoma (anterior part of the body) (Weihmann et al. 2012).  Cyclosa conica have muscles they are able to use to flex their limbs inwards, but have to rely on hydraulic pressure to extend their legs outward.  While the back legs of the Cyclosa conica are extended, to be able to move the front legs are then shortened so that the force is passed through the leg joints ventrally (Weihmann et al. 2012).

On the legs of the Cyclosa conica are long hair-like structures called trichobothria or setae.  The trichobothria on the legs help the Cyclosa conica to detect airborne vibrations and currents.  These hair-like trichobothria are useful to the Cyclosa conica because it allows them to detect any vibrations in their web.  The trichobothria of the Cyclosa conica are found on the tibia and only on the dorsal side where the tibia is exposed to air movements more frequently (Dudic et al. 2011).  The trichobothria on each leg are all arranged in a pattern.  Adult Cyclosa conica and their juvenile young have different amounts of setae or trichobothria on each leg but they both have the same trichobothrial pattern (Dudic et al. 2011).  The male and female Cyclosa conica have a difference in their trichobothria and trochobothrial patterns.  There is a similar arrangement of setae between the male and female but there is a difference on their pedipalps (the second pair of appendages that is near the mouth of the spider) (Dudic et al. 2011).   The male Cyclosa conica have a smaller number of setae on their pedipalps and also have an irregular distribution of trichobothria.  Female Cyclosa conica have a trichobothrial pattern and distribution on their pedipalps that is similar to the rest of their legs (Dudic et al. 2011).

Decoration in the webs is an adaptation for the Cyclosa conica to be able to catch more prey.  The Cyclosa conica is a type of orb-weaving spider which means they decorate their web with stabilimenta, or silk structures for decoration (Blackedge and Wenzel 1998).  The stabilimenta of the Cyclosa conica contains debris, like the remains or dead bodies of their prey or other insects.  The use of stabilimenta in the web was generally hypothesized as a way of camouflage, but has been found that the webs decorated with stabilimenta also attract more insects and increases the amount of prey.  A study conducted by I-Min Tso found that the Cyclosa conica were able to catch more prey than other spiders with webs that were not decorated.  Also from this study, the decorated webs were able to attract and capture almost 150% more insects than the webs without decoration (Tso 1998).  Web decorating also acts as a defense mechanism for the Cyclosa conica.  Stabilimenta was found to act as a defense against birds in a study conducted by Todd Blackledge and John Wenzel.  In the study they found that the birds would fly towards the web, halt and then fly away because the stabilimenta in the webs acted as a warning to the birds (Blackedge and Wenzel 1998).  The use of stabilimenta in the webs of Cyclosa conica help the spider to capture more prey and help as a defense against organisms that could potentially damage their web (Tso 1998, Blackedge and Wenzel 1998).


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