THE 17 YEAR CICADAS
This spring one of the most incredible insect phenomena will occur in our area; the emergence of the 17 year cicada.
As the soil warms up one foot underground, the cicada larva (immature insects) will release themselves from the tree roots that have been their source of nourishment for the last 17 years and begin their climb to the surface, creating little mounds of soil as they dig upward. There they will wait until the time is perfect. Then one spring day when the soil temperature reaches sixty-four degrees, millions of cicadas across our region will leave the ground and climb nearby trees. Once securely latched onto the tree the larvae will enter a period of metamorphosis soon to emerge as a transformed adult cicada.
Metamorphosis is a process in which an insect transforms from its larvae form into an adult often looking much different from the larvae. One good example is a caterpillar changing into an adult butterfly. In the case of the cicada the most notable change will be its clear wings.
As you walk though parks and fields you will see the 1/2″ holes the cicadas have prepared, patiently waiting underground for the correct evening to begin this timeless ritual. Temperature plays a key part in this timing.
Once full-grown adults, the masses of insects will feed on tree sap, clumsily getting used to flight, as they bang into each other and humans. This of course is very annoying to people. Animals including dogs and cats feast on the abundance of this prey and can gorge themselves until they get sick. It is important to keep a good eye on your pets at this stage. Thankfully cicadas are not toxic.
Rapidly the cicadas become good flyers and buzz around searching for mates. Noise to some and music to others, the whirring sound of cicadas fill the air. Luckily for us they settle down in the evening and are not active at night. Within six or seven weeks the process will reach its climax.
Female cicadas will find a branch often high in a tree to lay her eggs. There they chew a hole in the branch and deposit their eggs. Nymphs are the second stage of the cicada’s life cycle which are: eggs, nymphs, larvae and adults. There, the nymphs will grow until they are ready for the next major step. The young nymphs will fall to the ground at the base of the tree and dig down to attach to a root where it will live for seventeen years, waiting to start the process all over again.
Later in the summer, brown tree branches show evidence where this feeding has happened. This is a form of natural pruning and doesn’t harm mature trees. Young trees however can benefit from a protective covering. Cover small young trees with a protective cloth in June to guard them from the egg laying females. This will not be a major problem for mature trees which can survive a ‘natural pruning’.
The life cycle of the 17 year cicada is an incredible survival story. Appearing all at once in the millions is assurance that no predator would be able to get them all.
The sudden appearance of so many cicadas led early Americans to confuse them with the Biblical ‘locust’. Actually, true locust of the Bible are swarms of grasshoppers, not cicadas. The locust devoured fields of wheat and grain while cicadas survive on tree sap. This mistake remains common today as cicadas are often referred to as “17 year locust”.
This seemingly fool proof life style technique of the cicada has now come across an unpredictable problem. As millions of trees are removed from the environment by humans for development, vast areas of cicada habitat are disappearing. Along with the cicada, millions of other animals and birds are losing their habitat to mankind.
Get more information about this incredible wonder of the insect world from Rutgers Cooperative Extension fact sheet #220 entitled “Periodical Cicadas: 17 Year Locust”.
Happy Gardening,
James
