I feel bad for the people hunting everywhere for bagworms. One day I walked along and randomly shook a tree for the heck of it and a bagworm popped out xD
Just caught one by just hitting the trees with my net. definitely works! hit every tree in my town and nothing, went into a building and came out and started again and about half way through got one!
Make sure you hit the trees with the net from both sides. Otherwise you can still miss it. I hit the same tree from the left side twice and then randomly from the right, and then caught a bagworm that time.
And don't forget if you go inside a building, all insects reset so then you can go around again. There is an insect "limit" so once you make a circuit around the town no more will spawn until you scare some off or catch them, but this is time consuming and it easier just to wipe them by entering a building.
Oh my god I love you for this tip! Unfortunately I caught mine yesterday, after many bee stings Oh well, it will be useful if it definitely works with the spiders!