All

Dry Ice placed above the colony will kill bees quickly.  We've used dry ice 
for 30+ years for putting bees to sleep (they will wake up again, if the 
dose is small or of a short duration).

We also use dry ice to preserve samples (in the field).

In MT, you can buy it at any grocery store or even Walmart -- you may need 
it to get your ice cream home if you live in on a ranch in a rural area of 
MT.  Also, the out-of-state hunters buy it to ship their game home.

We've found it harder to find in more urban areas.  However, there are two 
places to check -- 1) any gas supply firm that sells gases for welding, 
oxygen to hospitals, etc., and 2) most any LARGE shipping firm that moves 
household goods.  They often have it since lots of people want to move 
their freezers full of food to their new house.  Personally, I'd clear out 
the freezer, send it empty and dry -- but apparently lots of folks don't 
want to leave the contents behind.

Jerry

P.S.  Remember to ALWAYS handle dry ice with gloves -- the ice can 
instantly freeze flesh.  Also, it lasts better in a sealed container (keeps 
moist air out).  Putting it in a fridge or freezer accelerates its 
sublimation due to the moist environment.  A room or outside air 
temperature, sealed storage box (pack any excess space with something like 
crumpled newsprint, tape the seams) will hold dry ice days longer than a 
fridge (the cold difference is insignificant when you consider the temp of 
the dry ice itself).

In a fiberglass reinforced, 3/4 inch plywood box with 2 inches of styrofoam 
insulation, I've bee able to keep a 50# block of dry ice for up to 2 
weeks.  (Needed when collecting samples in remote areas, don't leave the 
box open for any length of time, and if freezing samples, always place them 
UNDER the ice, cold moves downward).

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