I could actually use a few wasps in my backyard. That's not something people usually say, especially with small children, but here is the reason:
Now, the chickens may enjoy these little caterpillars, but my broccoli plants do not. I didn't use to think that there was any use for wasps, but I've found that having a few buzz around the garden is actually a very good thing. They eat these little caterpillars, which are so hard to see on the plants, and thereby help the broccoli, brussel sprouts, etc. As a bonus, the wasps have never bothered me or the kids during the gardening season, even when we are right by them in the garden. They are really focused on their food instead. Now, I don't want them in the house or making nests above my back door or anything, but I could use a couple visiting my garden on a daily basis. As it is, the kids and I pick off the caterpillars by hand and throw them into the chicken yard. The chickens love the treats, but if we don't check the plants for a few days (say, when we go out of town, or when the weather is abysmal), they can really wreak havoc on some broccoli.