there is a poisonous spider called the black widow that has a black almost shiny looking body with a red "hourglass" shaped red splotch on their underbelly. if that spider is the one your are talking about...it is poisonous. if you need to see a pic to make sure just look one up in Google images
There are a number of different spiders that could be described as black spiders with a red dot on their back including the Black Widow, the Australian Redback spider and the Jumping Spider.
http://en.wikipedia.org/wiki/Redback_spider
red back spider
The Black Widow Spider has either a yellow, red, or orange hourglass, but sometimes can look like a dot. Links: http://mysite.verizon.net/vzer75kc/
Could be a Black and Yellow garden spider, common the US west coast.
Some species of black widow have a red dot. A redback spider, the equivalent of a black widow in Australia, also has a red dot on its back. It is all black and quite small and has a big red patch on its back. it is highly venomous. See the related link below for a picture.
R u sure its not a spider that has a red dot on its back? If it is, then its probably a black widow. If its a white dot, then i think its poisnous. Stay away from it unless u wanna get biten or die.
The spider you are describing sounds like a black widow spider. These spiders are known for their shiny black bodies with a distinctive red hourglass or dot-shaped marking on their abdomen. They can be commonly found in dark, sheltered areas.
it might be the black widow...its nothing, just the most piosonous spider in the world xD
It may be a Black Widow spider. They are very poisonous and it is probably best not to approach it if you are unsure of the species. Black spiders have a distinctive red "hourglass" shape on its back.
I think that it might be a garden orb weaver, which is not dangerous, or a marbled orb weaver (which is in the same family). But, most of the pictures of this spider do no show it to be bright red....?
that would be a black widow. very dangerous. stay away from them. not a very nice spider to get bitten by! haha It isn't a black widow. Black widows have a red hourglass shape on their belly.