Those strange one inch “aliens” that are attached to tree trunks, fence posts and maybe even house siding are the cast skins of the dog day cicadas. They have been in the ground feeding on tree roots for the past 3 years. They often crawl up 1-2 feet on tree trunks and the skin will split and the green and black adults emerge. The plastic-like old exoskeleton (skin) is left behind.

Extension Bulletin