Re: Can you identify a type of spider for me.

To be sure I would need to see the specimen, but I can offer the following 
observations that might help.  First, I doubt that these are black widows 
because, although I have found one individual without markings in the past, 
I have never seen populations without some sort of red mark on the 
underside.   Even brown widows (Latrodectus geometricus) have an orange
hour-glass mark and red widows (Latrodectus bishopi) have a red bar on the 
underside. My guess would be a comb-footed spider (Theridiidae- same family
as the black widow) in some other genus, such as Steatoda.  Although one 
European species of Steatoda has been implicated in spider bite cases, none 
of the North American species has been to my knowledge.  There are other 
theridiid spiders that it might be, but I obviously cannot be sure unless I 
see the specimen

Ref: 

Kaston, B. J.  1978. How to know the spiders. 3rd ed.  Wm. Brown, Dubuque, 
Iowa.

Levi, H. W., and L. R. Levi.  1968.  Spiders and their kin.  Golden Press, 
NY.