Mealworm keeping

I use mealworms for feeding my black widow spiders (Lactodectrus).
The problem is that I don't feed the spiders more than every three
months.  It turns out that the 50-count meal worm container does not
last that long.  

Is there a way to keep meal worms longer or is it just a situation
where I have to get a new 50-count container every time I need to feed
the spiders?  I seem to be able to keep a male and female alive for
over three years.  This means a lot of wasted meal worms.

tnx,

Gary Gaugler, Ph.D.
Microtechnics, Inc.
Granite Bay, CA 95746
916.791.8191
[EMAIL PROTECTED] dot com