(This video was originally broadcast on Iowa Outdoors, Episode 403, July 3, 2014.)

If you have been outdoors lately, you may have heard the incessant buzz of the 17-year cicadas. It is almost deafening in some wooded areas. The periodical cicada is one of the most fascinating insects, spending all but a few weeks of its life underground, emerging to mate, reproduce and begin the 17-year cycle all over again.

(cicada sounds)

Take a listen.

(cicada sounds)

It's the summer sound of cicadas 17 years in the making. 

Heidi Anderson, Polk County Conservation Naturalist: All of a sudden they emerge at the same time and after that long it's amazing that they're able to synchronize all of that. And so it's really a unique occurrence that is happening right now. 

Donald Lewis, ISU Extension Entomologist: We have waited for this event, we have waited for this to happen for 17 years.

These insects are brood three of the periodical cicadas. They are found primarily in central, south central and southeastern Iowa. There are other broods of periodical cicadas that emerge in other years. And there are annual cicadas we see and hear every year. 

Donald Lewis: These periodical cicadas are related but they are different species than the annual cicadas and they only appear periodically. The body is smaller, the periodical cicadas are black, the wings have red or have orange veins and then they have these bright red beady eyes. So, they look different and they're on a different schedule. The periodical cicadas are here in June and July and they sing during the daytime. The annual cicadas are here from July to frost and they sing in the evening. 

Female cicadas lay eggs. Those eggs hatch into nymphs, which fall to the ground and then burrow themselves down into the dirt and attach to tree roots. They stay there feeding on sap from the tree root for 17 years before digging their way up to the surface. 

Donald Lewis: And then they go through the miracle of metamorphosis, where the insect actually crawls out of its own skin. So, a crack forms down the back of the insect, the cicada shell opens up and the insect pulls itself out.  

You can sometimes see piles of their hardened shells at the base of trees or on plants. 

Donald Lewis: And in the tree the males sing, they do that with a drum on the side of their abdomen. The males are singing, that is a signal to the female that I'm over here. And once the female has mated, she lays eggs and we start the cycle over. 

You'll find periodical cicadas primarily in native woodlands or in areas with older tree populations. There can be a million and a half periodical cicadas per acre and as many as 40,000 of them in a single tree. 

Heidi Anderson: And it has been a full out chorus everywhere in the park of the cicadas calling to try to find a mate. And it is, can be very loud in certain areas and sometimes my co-workers, we almost have to shout to each other in some places because they're just so loud. 

(cicada sounds)

Donald Lewis: Just the singing of all those tens of thousands of male cicadas is annoying to people who have to be around it all the time. 

These insects are mostly harmless. They will not bite or sting and they pose little threat to plants or trees. They do not have chewing mouth parts and they feed only on tree sap.

Donald Lewis: Not damaging to crops, not harmful to people. It's an insect that almost everybody can love. 

The rare, unusual characteristics of this long-living insect are fascinating to entomologists. 

Donald Lewis: We could almost sell tickets and bill it as a tourist attraction because there are people who are fascinated by cicadas, there are people who are fascinated by insects. I was here when the grandparents of these cicadas emerged back in 1980 and it was such a phenomenon to see them that I couldn't wait for it to happen again in 1997. Here I am in 2014 seeing them again. I hope I'm around to see it one more time in 2031. 

Since the periodical cicadas only come around every 17 years, you can look at them two different ways. If you like them, get out and look, listen and enjoy them while you can. Or, if they annoy you, take comfort in knowing that they'll soon be gone and won't be seen or heard for another 17 years. 

Gilchrist Foundation