Social spiders, fact or fiction?

A few species of spiders that build webs live together in large colonies and show social behavior, albeit not as well evolved as in social insects. The most social species is probably Anelosimus eximius, which can form colonies of up to fifty thousand individuals.





so if they are less evolved, would that simply imply cannibalism? or a lesser degree of cooperation such as ants?





imagine walking through the forest in the dark and getting entangled in one of these? http://www.loria.fr/~bourjot/toile.jpg

Social spiders, fact or fiction?
Unusual sociability found in whip spiders


http://www.sciencedaily.com/upi/index.ph...





"on the evolution of social and sexual behavior in animal taxa ranging from ... Reproductive behavior of the spider " http://biology.unm.edu/Biology/pwatson/p...





As stated, cannabilism is not an evolutionary trait. It is a behavior, usually brought on by over population or extreme competition.
Reply:Cannibalism refers to the practice of consuming one's own for sustenance (food), and while it can be argued that the practice may seem acceptable in cases of pure survival, I can not envision how this practice could be referred to as a form of evolution, except maybe in a strange way, perhaps it was something else you were thinking of?


Either way, I think it involves a lesser degree of cooperation, yes, such as ants.
Reply:Ants, bees, and termites have an elaborate system for division of labor, with only one female per colony reproducing.


I think the social spiders do not engage in this division of labor, or at least I have not read about it if they do.


They share in the tasks and share the food; they group their egg sacs together and share the care-taking; and so forth. But the colony members are quite capable of reproducing if removed from the colony, which is not the case with the social insects.


They probably do engage in some cannibalism, though this is not a factor in how "evolved" their "social structure" is. It is common for baby spiders to eat their siblings until they are big enough to catch something else. Spiders are not sentimental.


However, since social spiders share food, this is probably not often necessary for them. Less cannibalism would also result in greater numbers of surviving offspring.


And for a large spider colony to survive, there must be a tremendous amount of prey in the environment!
Reply:There are several level of sociality known in


various kinds of animals. I won't attempt to


explain them here because I haven't my references at hand. However the social spiders


show much less well developed sociality than ants and termites.





Willis Gertsch, the former spider expert at the American Museum of Natural History was once


asked what was the largest spider web he had


ever seen. His answer was "Ten feet high and


200 miles long." What he was referring to was


probably the semi-social spider I have seen in


northeastern Mexico where the webs are built


from the rather low telephone wires to the ground. When the population is high these webs


are in contact with each other for varying distances. He had apparently seen them at a time when the species was very abundant.





In th south Pacific the communal orb-weaver


Cyrtophora moluccensis builds huge tangles in


which each spider has its own orb-web suspended. A small communal web of this kind


that was examined carefully contained hundreds


of the spiders. On the island of Guam, when the


population was high one could see what looked


like clouds of smoke hanging over clumps of


trees. These were enormous communal webs


of the spiders, which must have contained


thousands of Cyrtophora, as well as inquiline


spiders of other kinds which also occur in the


webs.
Reply:Fact


But few and far between





Less evolved would not imply cannibalism, however some spider species are already known for females killing the males in the process of reproduction.





I think that Less evolved would probably mean that their form of cooperation is not as highly specialized as perhaps that of bees communicating with each other - or even ants communicating with each other.





I would be so freaked if I got caught in a web like that. Spiders give me the creeps!





Oooh - the last link is to a french article where they were studying cooperation in prey capture in A eximius. You might be interested.