The ichneumon wasp lays its eggs in the larvae of the bag worm. Eggs hatch, larvae dies, bag worms do not infest our trees. The ichneumon wasp is attracted to flowers of the aster family so, presumably, if you plant asters, you encourage ichneumon wasps which discourages bag worms.
I found a real life example of this when we were waiting for my cousin Terry and my aunt Joan last week:
The wasp is kind of in the center of the picture, getting ready to fulfill its calling as a bag worm predator.
Pat and I spend many an enjoyable hour on our screened in back porch. There is a ceiling fan, which helps make the 90 degree temperatures bearable.
From our porch we can see our butterfly garden, our bird feeders, bird bath and hummingbird feeder.
We were enjoying a nice lunch out there the other day and noticed one of our many bluebirds was sitting on top of the bird feeder.
Suddenly it swooped down toward the butterfly garden and snatched a sulphur. The bluebird flew over to our split rail fence (soon to be the home of our lush, heavy laden grapevines, tho' something is eating the leaves now)* and sat there with the poor little butterfly in its mouth. It smashed it on the fence a few times and then finally ate it.
We were shocked.
We were not expecting such violence in our backyard.
Then the same scene repeated itself. We were starting to regret planting a butterfly garden.
poor little blurry sulphur has no idea what is about to befall it
(I have a hard time getting a good focus in full sun)
We also recently put up our hummingbird feeder. We really get the hummingbirds coming in here. We have seen four or five at once and man, are they mean to each other. It sounds like Star Wars out there sometimes with the light saber sound of their wings beating. Their chirping sounds like Flipper. Retro TV and film sound effects all at once.
The other day some of them were really going after each other. For a brief moment during the fray, one of them got their beak stuck in our screen porch. A little comic relief. It disengaged itself in short order and went on to fight another day.
This is how we entertain ourselves. This entertainment, though natural, is a little more violent than I like. I prefer comedy. For that, we go down and visit Mom and Dad. :) Love you guys!
*I suppose I should not use the word 'lush' and grapevine in the same sentence. We are hoping to have grapes to eat, make jelly and perhaps grape juice of the non-fermented variety.