When most people use the term ‘dog days,’ they are referring to days so hot and muggy even dogs don’t move. The term comes from the astronomers of ancient Greece. There is a star in the constellation Canis Major (the Great Dog), positioned in the outline of the dog’s nose, called Sirius or the Dog Star. In the northern hemisphere this star rises just before the sun in July, marking the start of the hottest days of summer, which is how the “dog days of summer” phrase originated. So, here in Minnesota it’s fitting to call the annual cicadas the “dog day cicada” since we start hearing their high pitched droning call early in July.
While cicadas are frequently heard, they are rarely seen because adults spend their time high in the tree tops. Cicadas are a large insect, up to 2” long, with a black body, brown and green markings and green veined wings. Perhaps more commonly seen are the amber-brown nymphs that live underground, and occasionally the adults drying out after casting their exoskeleton. These cast skins shed by the nymphs are found regularly on trees and at first glance look just like the complete insect.
Cicadas are in a family of insects considered to be true bugs. Their life cycle or metamorphosis is categorized as simple, going from egg to nymph to adult. After mating, the female lays her eggs in living tree branches by cutting an opening in the bark. Eggs hatch into nymphs and fall to the ground where they burrow into the soil, up to 8’ deep, and live for 2-5 years. While in the ground nymphs feed on tree roots, but unlike some cicada species, annual cicadas are not pests and do not cause any injury to the tree roots they feed off. After years underground the nymphs emerge, shed and climb to the top of the tree.
In the U.S. all cicadas are often thought of as periodical cicadas that have a 13 or 17 year cycle where the adults are only present in those years. This cyclical emergence of nymphs metamorphosing into adults once every 13 or 17 years is called synchronized development. Here in Minnesota, instead of periodical cicadas we have the annual or “dog day” cicadas. So the call of the cicadas is part of nature’s soundtrack every summer starting in July and going into September.
The adult male is the only one to sing and will do so from treetops, trying to court a female to mate. Their song, among the loudest of all insect-produced sounds, is a humming noise like a pulsating buzz. The sound is loud enough to cause permanent hearing loss if a cicada was calling next to a human ear. It’s produced by rapidly vibrating membranes that produce clicks combined into seemingly continuous notes. The male’s abdomen is mostly hollow so the sound can resonate and an enlarged trachea chamber amplifies the sound. The song can be changed and different patterns created by moving its abdomen closer or further to the tree in order to attract appropriate mates.
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Are you curious to learn more about insects? Join us on July 15 for our A Prairie Home public program. Or stop by the front desk to borrow an insect net and jar to seek out cicadas and other insects in the park yourself. Sign up kids ages 6-12 for summer camps such as World of Insects and Down in the Dirt to take a closer look at our six-legged friends. Camps run each week Monday-Friday, 8 a.m-4 p.m. in two different themed sessions (8 a.m.-noon and noon-4 p.m.). Register online or call 612-370-4844. Fee waivers available, call for application details.
July Free Public Programs (all ages):
July 8 – Early Birding: Search for birds while on a naturalist-guided hike. 9-10:30 a.m.
July 15 – A Prairie Home: Hike through the prairie to catch and identify insects. 1-3 p.m.
July 22 – S’mores Galore Family Game Night: Play outside games, roast marshmallows and enjoy a campfire. 7-9 p.m.
Visit our Nature Exploration Station at the playground throughout the week!
For info or to register for programs at North Mississippi Regional Park visit minneapolisparks.org and like us on Facebook to stay in the loop about what is happening at our park!
Written by Kelley Ekstrom, Minneapolis Park & Recreation Board Naturalist at North Mississippi Regional Park