Collecting earthworms on the sidewalk or road after rain is the worst place to collect. That is where most of the pollution flows when it rains. I have used wc insect and when my dart frog colection was in great numbers I was filed sweeping every other day up in a rural area. I would avoid farmlands, the city's and any commercially mantained areas, I used private pasturelands and areas in the state park to colect other micro fauna.

Michael