Subject: When 2 slugs are hanging, intertwined. are they mating?

We saw 2 large slugs (about 4-5" long) haging upside down from a strand of goo 
on a post, intertwined, with a whitish glob of something hanging down below 
their heads.  This glob appeared to be moving/gyrating at times, and was 
actually almost blue-ish in color.  The glob was thicker around the middle area 
(like a heavier band around it), at least 1" in diameter, and was attached to 
both slugs by a "string" of the whitish stuff.  This "string" came from behind 
the head area, on the side.  We thought they'd hang there for some time, but we 
turned our backs for what could not have been more than 2 minutes, and they 
were untwisting, and the glob was gone.  What was that???  One other thing, 
there was what looked to be a hole on the side of these slugs, further from the 
head than where the strings appeared to be coming from.  

Re: When 2 slugs are hanging, intertwined. are they mating?