If you're seeing unusual looking mud tubes protruding from the ground in the spring are you probably looking at cicada chimneys and these signal the appearance of cicadas is near. The chimneys usually appear after a rain shower which can flood a cicada nymph's underground borrow. The structures are made of dirt, cicada spit, and whatever the insects find lying nearby. And, these chimneys are made by lots of different cicadas, not just the 17 year cicada.
Cicadas may give away their pending emergence by building thousands of 'chimneys' or 'stovepipes' made of mud on the ground, especially near trees. ***image1***They will emerge through these structures when they leave the ground and crawl up trees and shrubs.
During the spring of the emergence year, periodical cicada nymphs may build mud tubes that project three to five inches above the soil, apparently to escape wet or saturated soils. These tubes are often mistaken for the tubes that crayfish build.
Periodical cicadas emerge in specific locations once every 17 years in the northern part of their range, and once every 13 years in the southern part. Different groups called "broods" emerge somewhere in the eastern United States almost every spring.