By Staff
If you haven't been keeping up with the bug news, you might be in for a big surprise here in the upper Midwest.
This is the year for emergence of the 17-year cicadas in this area. The enormous size and even more enormous quantity of these hulking honkers could freak out those afflicted with bug paranoia.
Cicadas are big, as in a broad, boxy-looking, one inch long with transparent wings folded over the top of their bodies. There are several dozen cicada species and all have quite long life cycles, at least as far as bugs go.
In most species, the larvae live underground unseen for two to eight years before they finally emerge as adults. These emergences are not synchronized so we have some cicadas coming and going every year. These species are grouped together under the heading of annual cicadas. Not much to get excited about there.
It's the other grouping consisting of seven cicada species that provide a real event. These are called the periodical cicadas. They emerge only once every 13 years or 17 years, depending on the species.
The 13-year species live further south and are not scheduled for this year so we won't concern ourselves with them. It's the 17-year cicadas that are scheduled to appear here in the upper Midwest. Their emergence is synchronized on a regional basis so on a given few nights they all emerge at once, seemingly taking over the world. This emergence is expected in southern Michigan, Indiana, Illinois, southern Wisconsin and Iowa.
It started earlier this month in the south of the region and is working northward as the soil warms. So what do I mean by lots of cicadas? In the heaviest populated areas there can be tens to hundreds of thousands per acre with record emergences reaching up to one and half million per acre. For you non-farmers an acre is 210 feet by 210 feet, less than two football fields. That's a lot of bugs, especially when they're the size of winged cows!
The prolonged life cycle of 17-year cicadas is unique. The nymph lives in an underground burrow ranging from a few inches to a few feet long, sucking the juices from roots for sustenance. Here it stays for the obligatory 17 years, going through five molts, as it grows larger. On a warm spring evening of the final magic year it digs an exit tunnel and crawls above ground.
The timing is believed to be triggered by soil temperature reaching 64 degrees. This explains how all the cicadas in an area emerge at the same time. The nymph crawls to nearby vegetation and molts into an adult cicada. At this point the outer shell is soft, which is called the teneral stage. The teneral adult makes its way into a tree where it simply hangs out for the next few days waiting for its shell to harden. Then they're finally ready for business.
For the next month or so the males gather in groups in the tree tops and begin "singing" to attract the girls. This is the familiar buzzing sound all cicada species make with special structures in their abdomen called tymbals. The songs are very complex and specific to the species. These tree top concerts can become very large, especially as the gals begin showing up to check out the choir boys. Once mated the females excavate Y shaped nests in living twigs, laying about 20 eggs per nest and up to six hundred eggs in all. In six to 10 weeks the eggs hatch, the nymphs fall to the ground and dig their burrows where they will reside for 17 years.
The size and number of the adult cicadas may wig us out but they are harmless. They don't sting, bite or transmit disease. However, if enough of them gather to dine on a small tree or shrub they may cause some damage to the plant. There are often too many cicadas for pesticides to be effective. If there are concerns cover the plant with some sort of screening like cheesecloth until they move on. Carpe diem.