Can all spiders traverse all kinds of webs, or is the fluid the webs are made of fundamentally different across species, so one species of spider would get caught in the web of another species of spider? I wonder how often a spider might wander away from its own web and get caught in another, since the cobwebs I see forming all around the house never actually seem to be guarded by the spiders that must have made them. Also, I heard that many spiders are cannibalistic in nature, so they'd be more than willing to devour another spider if, say, a fly doesn't come buzzing along. Thanks!

Hi Joe,

Its a little difficult to answer as I'm not sure there is a specific answer possible. As i see, it is rare for spiders to get caught in the webs of others. For example, many webs are setup to catch flying insects which get mixed up in the strands as they struggle. As spiders dont fly, there is little chance for them to get stuck in the middle of another setup web. 

So, indeed we have to think about wandering spiders, and tangling in other new and old cobwebs lying around. So, the legs of most spiders have hairs that prevent direct contact of the exoskeleton with webs, and i suggest that most don't get caught in webs of others. But, it can and does happen, and if there is another hungary occupant, then that's lunch sorted. Sometimes i see wandering spiders with bits of web stuck to a leg or two, that means it escaped, but there is still some of the web strands attached to it, onto which it mistakenly got trapped into. But not trapped enough..

Most cobweb makig spiders are either very cryptic (ie like well camoflaged) or vary wary. Many are nocturnal hunters, only coming out of hiding places at night, so you might have little chance to see them, even if there. Also, it is common for adult male spiders to wander away from webs/home territories when they mature to adulthood, as they go in search of females. These leave old webs behind to become cobwebs.

I think many wandering spiders are able to avoid being ensnared in webs of others. In general local spiders put special signalling molecules onto the web strands to provide sensory marker to others. For example, male spiders might be able to detect if there is an interesting female spider of the same species in a web it comes across, just by touching the web strands, and picking up the chemical signals there.

Hope that helps. There are indeed many spiders that hunt other spiders, and some of these have to deal with extracting the target spider from its web. There is a great and very smart type of jumping spider called Portia that actively hunts several other types of spiders. To be described as a cannibal it has to eat its own species, which in general is rare, but spider predators on others spiders is rather more common. Its a tough enough world for most spiders..., without some humans trying to get rid of them too!

Last edited by Stuart Longhorn (22nd Apr 2010 18:20:16)

To add to Stuart's answer, there are also spiders that will steal prey and even silk from other spider's webs in order to eat it - spiders in the genus Argyrode specialise in this (Higgings & Buskirk, 1998). Obviously this means that the kleptoparasitic spiders must be able to manouvre on the web of their host without beoming entangled.

To the best of my knowledge this is achieved in the same way by the host and its thieving web-guest - they simply don't step on the blobs of adhesive that are spaced along a piece of web (the web itself is smooth silk, the stickiness comes from additional adhesive blobs that the spider adds to the trap section of the web). If they do hit a blob they can tug their foot free since the adhesive isn't really that strong, the spiders are relying on flys hitting lots of blobs to become stuck.

Higgings & Buskirk. 1998. Spider-web kleptoparasites as a model for studying producer-consumer interactions. Behavioural Ecology, 9:384-387