You may have seen, in the national news, a story about a big swarm of cicadas expected this summer. Here are some of the facts concerning this event.
The cicada is a large and harmless insect with 2 pairs of membranous wings and a beak for piercing and sucking. All animals have mature and immature phases in their life cycle but, what’s unusual about this insect is that some species, in this family, spend 17 years in immature stages in the soil and a few weeks as mature adults, high in trees. Several broods of the genus Magicicada have been identified and their life cycles recorded. In one of the largest of them, known as brood II, a massive emergence of the adults of this brood occurred in 1996. This means that the generation that they produced is due to emerge this year, and that has already started to happen.
The wingless nymphs have spent the last 17 years feeding on roots in the soil and growing through several instars. Then, on a series of nights, early in the season, a bunch of them emerges from the soil. They climb several feet up a tree. Then, clinging to the trunk, the winged adult emerges from the nymphal skeleton. By morning, blood has been pumped into the wing veins and they are able to fly off to near the top of the tree. The shed nymph skeleton can still be seen, clinging to the tree trunk. The adult males vibrate sound organs on their abdomens, making a buzzing sound to attract females. Where there is a large emergence this year, there’s so much of this buzzing, making it so loud, that hikers have a hard time hearing each other. The eggs drop to the ground and the little nymphs hatch out and go underground for another 17 years.
While we have cicadas here, and you might hear them and see the nymph skeletons on trees during our next few hikes, this particular brood is not known to occur in this area. If you go to the web site, www.magicicada.org, you can bring up maps showing where they occur and where they have been seen emerging. In case your travels take you there in the next few weeks, you can be treated to a rare and interesting natural phenomenon.