I don't know what species you are dealing with, but where I grew up
   (near Vancouver, B.C.) the mud wasps gathered spiders (the ones with
   typical aerial spider webs) and filled the mud tube with 10 to  20 of
   them, paralysed. A wasp larva sealed in the tube had its whole food
   supply available, and would attach to one, suck its juices, and the next
   was just beside, still fresh. The new generation (only about 10 to a
   group of tubes, I think) stayed there through the winter and emerged the
   next spring. The wasps were never aggressive (I don't know of anyone
   being stung by one, but I didn't stick my nose too close). They made an
   interesting  sound as they vibrated a load of mud onto the tubes they
   were building.
 
   So what "good" were they?
 
   To reduce them to numbers, they were no doubt one of the checks and
   balances in the predator - prey interaction involving flies.
   Or maybe they could just be appreciated for doing what they otter, in
   making a living.
 
 
   Kerry Clark, Apiculture Specialist
   B.C. Ministry of Agriculture
   1201 103 Ave
   Dawson Creek B.C.
        V1G 4J2  CANADA          Tel (604) 784-2225     fax (604) 784-2299
   INTERNET [log in to unmask]