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]