August
Cicadas
17 year periodical cicada
Life in the thick heat of late summer moves to the soundtrack of the dronning cicada. Though the hum surrounds us, there’s often little known about the cicada’s life cycle and the details of their habits.
Wisconsin has nine known species of cicada but worldwide there are approximately 1500 known cicada species. The one pictured above – the 17 year periodical cicada – is perhaps most famous because adults mature and emerge in a synchronized fashion after spending seventeen years underground as immature insects (more on that later). These broods of surfacing songsters have been named and tracked over the years.
Parts of Wisconsin are host to broods III and XIII which will next see the light of day in 2031 and 2019, respectively. More common on an annual basis is the Dogday Cicada whose name is a nod to the hot, “dog days” of summer (which in turn is a reference to the dog star, Sirius, which rises above the horizon at sunrise this time of year). While the Dogday (and other annual cicadas) are distinguished from the 17 year by green and brown coloration and a lack of red eyes, the best way to accurately identify cicadas is by their call, as each species’ is unique.
The sound they create is designed to attract a mate. Male cicadas use muscles to vibrate a set of drum-like membranes, called timbals. These timbals are located where the thorax and abdomen meet, and the mostly empty abdomen acts as a resonating chamber.
Whether spending seventeen years or four underground, all cicadas go through the same life cycle. Beguiled females who respond to the mating call of the males, use an ovipositor to cut open twigs and deposit their eggs within. (By the way, this may be the cause of small branches with faded leaves found on your lawn, since the cutting process can damage branch tips.)
Once the eggs hatch, the youngsters, known as nymphs, drop to the ground, bury themselves, and spend their designated time feeding on the sap of tree roots. The cicada (along with several other insect species) does not form a pupa (or cocoon/chrysalis) in their life time. Instead, they go through several nymphal stages, shedding their exoskeleton at each stage.
It is the final skin shedding that reveals the winged adult insect which only lives for a few weeks – long enough to sing, mate and start the life cycle anew.
Did you know…
Cicadas are not in the locust family as some believe, but are in the insect Order of Hemiptera (which means half wing). This family of insects, which includes aphids, leafhoppers, and boxelder bugs, is also known as “true bugs.” They are distinct from other insect families because of their half wings (the front wings are half hard shell like a beetle’s, and half membranous like a dragonfly’s). They are also known for their non-retractable, straw-like mouth parts, and for going through incomplete metamorphosis, as mentioned above. Find more info on true bugs from Arizona State University.
While most Wisconsin cicadas are diurnal (active in the daytime), a debate in our neighborhood regarding nighttime sounds, spurred a further bit of research.
Here is the sound of the Common True Katydid:
And here is the sound of the Eastern Gray Tree Frog:
Both are nocturnal and vary from the sound of the diurnal Dogday Cicada:
To Do This Month:
Look for the exoskeletons of emergent cicadas – or try to spot them in action as they emerge from their nymphal skin with these tips from Massachusetts Cicadas. Brush up on more cicada knowledge with Cicada Mania, a website devoted to all things cicada or, read UW Milwaukee Field Station’s Bug of the Week bio. Also try searching for Cicada Hunt in the app store for a bug-listening app that just might identify what you’re hearing.
Learn about edible insects (and maybe try a few, too!) at Madison Children’s’ Museum August 11th, 2015, or visit a Madison Conservation Park to look and listen for insects along the trail. Be sure to catch the final days of Olbrich Garden’s Blooming Butterflies and stop by Aldo Leopold Nature Center to check out the Gardens & Greenery phenology activities.
Our Favorite Insect Books
August Events
Madison Conservation Parks
Cicada Craft – for real!
For Educators:
Forestry Education Kit
While the cicada song may have dwindled or stopped altogether by the time the first school bell rings, there’s still plenty of insect inspiration in our forests to stimulate classroom lessons and exploration. LEAF, Wisconsin’s K-12 Forestry Education Program, makes this charge easy with their Forest Health Kit – available through a free check-out system. The kit includes a set of insect nets, collection tubes, and a rearing and observation cage.
Several insect, spider, and fungi books are included, as are information sheets and lesson ideas. A few of the lesson plans are available on-line, including a middle-school unit that encourages students to imagine forest management issues and decisions; and a lesson on earthworms that invites students to become citizen scientist and report data on worms to the Wisconsin Department of Natural Resources’ Wisconsin Worm Watch. Delve into topics beyond insects and worms with your kit, including invasive species, disease, and climate.
If your school does not have an outdoor grounds to explore with your kit materials, you may find one of Wisconsin’s 412 school forests nearby or visit a Nature Net site that offers guided insect tours. You might also consider a classroom visit from the UW-Madison’s Insect Ambassadors, who bring Walking Sticks and Madagascar Hissing Cockroaches for children to investigate.
UW’s Insect Ambassadors also provide an extensive list of classroom activities, citizen science projects, and suggested reading. And BiologyResources.com offers free downloads of annotated drawings and life cycle info sheets.
After you hit the trails with nets in hand, check out InsectIdenification.org or UW-Madison Entomology Department’s Insect ID website to discover what you’ve collected and learn more about each species.
For Families:
Cicada Collections
Entomologists who study insects for a living base their work on specimens that are often collected, euthanized, and then dried and pinned for careful handling and observation. For those who can’t stomach the euthanization part, collecting cicada shells might be the perfect answer for budding scientists.
In some cultures, including in Japan, collecting cicada exoskeletons is a rite of summer – they are considered a symbol of evanescence, since the adult cicada has such a fleeting lifespan.
Look for skin sheddings still clinging to tree trunks, fence posts, or littering the ground at tree bases. Check out these pictures of a nymph emerging and the adult cicada leaving the exoskeleton behind to know what to look for. The scientific name of these lifeless shells is “exuviae.”
While you’re on the search, you might also find the exuviae of other species who molt this way, including dragonflies, damselflies, and mayflies.
If you do feel prepared to create an insect collection with pinned specimens, here a few tips to get you started with children. In the meantime, here are some funny ideas on what to do with dead cicadas or their shells.