This mating couple seems to disagree on which way to go.
In the last episode of Bug of the Week we learned about the rock concert in the treetops, the hallmark chorusing of male periodical cicadas. Using paired acoustic organs call tymbals, males produce a variety of calls, one of which assembles males and females of the same species in large aggregations called chorusing centers. Chorusing centers are often located in large trees and clusters of adjacent trees. When guys and gals get eye to eye, the male will use three distinct and different courtship songs to woo his mate. If the lady likes his advances, she will signal her approval by flicking her wings with an audible click. After mating, the female cicada moves to tender young branches to lay eggs. Using a hollow saber-like structure on her abdomen called an ovipositor, the female gouges groves into the woody tissue and lays 20 to 30 eggs in an egg nest. This process may be repeated on several branches and on different plants.
Each slit marks the spot where a cicada dug into a tender branch to lay her eggs.
Fecundity is estimated to range from 400 to as many as 600 eggs per female. With an astounding reproductive potential like this, it is easy to see how a single widespread cicada brood might contain tens of billions of cicadas. More than 80 species of woody plants may be used as hosts by egg-laying females, with angiosperms (flowering plants) greatly preferred over gymnosperms (conifers, cycads, Ginkgo, and Gnetales). While the mere presence of adult cicadas poses no threat to humans, the egg-laying behavior of females can damage trees, especially young ones whose canopies are comprised of many tender young shoots. This damage may dramatically change the normal growth habit of the tree. Egg-laying may also weaken branches and cause them to hang down (flag) or snap from the tree. Methods to protect small trees from cicada damage were described in the Bug of the Week episode entitled “Brood II up in Maryland” on May 13, 2013.
With pulsing abdomen, a female cicada injects her brood into slits in a branch through a tubular appendage called the ovipositor.
Eggs develop in the branch for more than a month before hatching.
After incubating for more than a month, eggs hatch and tiny nymphs just a few millimeters long dive to the earth. In a matter of minutes, they burrow into the soil, find a root, and insert their small straw-like proboscis. In addition to feeding on roots of woody plants, herbaceous plants and grasses are also used as sources of nutrition. The low nutrient content of xylem fluid may help explain in part the very long period of juvenile development of cicada nymphs, which is thought to be the longest in the insect world. For the next seventeen years, Brood II cicada nymphs will hunker down underground sipping fluids from xylem tissue and slowly growing larger while they await their return to the sun in 2030.
After dropping to earth, tiny cicada nymphs burrow underground and attach to the roots of plants to feed.
References
The wonderful article “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon and the informative bulletin “Periodical Cicada” by Greg Hoover were used as resources for this episode.
To learn more about periodical cicadas and cicadas in general, please visit the following excellent web sites:
http://insects.ummz.lsa.umich.edu/fauna/michigan_cicadas/Periodical/Index.html
http://www.cicadamania.com/cicadas/category/broods/brood-ii/
To see the Bug Guy’s attempt to explain cicadas to Jay Leno and Russell Crowe, please visit the following links:
Part 1: http://www.nbc.com/the-tonight-show/video/cicada-expert-professor-mike-raupp-part-1/n37779/
Part 2: http://www.nbc.com/the-tonight-show/video/cicada-expert-professor-mike-raupp-part-2/n37780
Be sure to watch 'Cicadas and Invaders' on the Science Channel: