Re: why are some spiders furry and does it help them stay warm?

Dear Jake,

That is a good question.  The reason spiders do not get cold is because
they are not warm blooded like other animals with fur. The "fur" that
you see on tarantulas and other spiders is not really hair but "bristles"
and has nothing to do with how a spider keeps warm.  The "hair" on a spider
is used for several reasons.  The hairs on a spider sense vibrations and a
spider can tell a lot about it's enviroment from what it senses in theses
hairs.  Some spiders, like many New World tarantulas can use some of their
hairs for defense.  These urticating hairs are itchy and when a predator
comes to close they shoot these hairs to make the predator go away.

So, back to your question, how do they keep warm?  Well, spiders are
cold-blooded (actually, their blood is called hemolymph and is different from
reptiles, etc).  Spiders are the same temperatures as their surroundings
and different species are adapted for different surroundings. when they are
cold they will move to a warmer spot and if they are cold they will move to
a warmer spot.  Some spiders lay their eggs in Fall and then die and their
eggs hatch in Spring.  Other spiders dig burrows deep in ground and stay
there all winter. The spiders that live in your house live there because
the temperature is comfortable to them.  Some people find spiders in their
house and put them outside.  This is not really a good idea because house
spiders are adapted to live inside and can't survive outside.  But, it's
good to have in your house because they eat all insects like roaches, etc.
that might carry diseases.

I hope this helps you, Jake.  I think it is really great that you are
concerned about the spiders living in your house.  

Sincerely,

Elizabeth A. Mule

References:  

Foelix, R. (1994) The Biology of Spiders. Oxford University Press
Schutz, S. and Schutx,M. (1998) The Tarantula Keepers Guide. Barron's    
   Educational Series