This year, parts of Maryland will experience another cicada invasion when Brood II emerges from the ground.  Periodical cicadas are grouped into broods based on the calendar year when they emerge. The different broods have been assigned Roman numerals to identify them.  Cicadas spend most of their lives underground feeding on xylem fluids from the roots of deciduous forest trees in the eastern U.S. After 13 or 17 years (depending on the brood), mature cicada nymphs emerge in tremendous numbers, digging their way up once the soil temperature reaches about 64 degrees. After this prolonged developmental phase the adults are active for about 4-6 weeks. They emerge for one purpose--to mate. During their time above ground you'll hear the males broadcasting their shrill mating calls.   The females lay their eggs inside cuts in tree branches. After this, the adults die. About 2 months later, the eggs hatch and nymph cicadas drop to the ground, burrowing beneath tree roots that they feed on until the next cycle begins.

Cicadas are actually quite beneficial to the ecology. Adult cicadas cause virtually no feeding damage. The only damage caused to plants results from the egg-laying habits of the females. The females cut V-shaped slits on the bark of young twigs and lay their eggs. This can serve as a natural "pruning" of the weak branches of a tree. These weak branches will wither and die and the tree benefits by not having to waste energy on a weak or diseased branch.   Another benefit to trees is when the cicadas die they release a vast amount of nutrients back into the soil. It's like dumping bags of fertilizer around the roots of the trees.

You may wonder "what's the point?"  In addition to the nutrients they provide to trees, cicadas provide a link in the food chain between trees and animals. Many animals love to eat cicadas and their emergence is like one huge feast for many critters. The massive release of food and energy that comes from the cicada emergence results in a population explosion for the small critters that eat them. This in turn results in more food for predators as well.  Many people around the world also prepare and eat cicada, and some consider them quite a delicacy. 

Cicadas pose no health threat to people or pets. They won't bite and if they land on you it's purely accidental. In general, it does not hurt cats or dogs to eat cicadas. However, it's best to discourage this activity as consuming too many cicadas at one time can cause problems, since their non-digestible skins could block portions of your pets' digestive tract.

So, while some people view cicadas as a nuisance, if you think about their incredible life cycle and realize that they really do serve a purpose you might view them as one of the wonders of nature instead.

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