A late night sortie may reveal a newly emerged adult and its shed nymphal skin.
The emergence of Brood II periodical cicadas in 2013 was a spectacle for all, a nightmare for some, and an entomophile’s dream. Bug of the Week visited these remarkable creatures several times during the magical spring and early summer of Brood II. Whereas 2013 was a raucous display of cicada power, the hot and humid dog days of July and August 2015 have delivered a most delightful ensemble of cicadas melodically singing their hearts out.
Maryland is fortunate to have more than a dozen species of cicadas appearing each year. Most of the treetop troubadours in Maryland are members of the genus Neotibicen, formerly known as Tibicen. The dog day cicadas share much biology and behavior with their periodical cousins. The immature stages, called nymphs, spend years underground feeding on the sap found in the roots of plants. Fully developed nymphs emerge, usually after sunset, and move from the soil to upright structures such as trees, shrubs, or the sides of buildings. The nocturnal emergence is likely a way to avoid detection by day-hunting predators such as birds and squirrels when these soft-shell cicadas are most vulnerable to attack. The nymphs hold fast to a plant and their exoskeleton splits along the midline, enabling the adult cicada to emerge. Gorgeous newly emerged cicadas must wait several hours for their exoskeleton to harden. Usually by sunrise the dog day cicadas are ready to fly.
After shedding its last nymphal skin the adult cicada must wait for its exoskeleton to harden before it can fly.
Once in the treetops, males vibrate a drum-like membrane called a tymbal to create their shrill song. The song is unique for each species of cicada and the female uses the chorus to locate and select a worthy mate. Males can use the tymbal to create a startling squawk call if harassed by a predator or a bug geek. After mating, the female cicada inserts tiny eggs into small branches of trees. After a month or so, eggs hatch and the nymphs dive to the ground and burrow into the soil to feed on the roots of trees and shrubs.
The dog day cicadas belong to a group of cicadas known as annual cicadas, which typically emerge in the hot days of mid- to late-summer. Annual does not mean that they spend only a year underground as nymphs. The term annual refers to the fact that these cicadas are seen every year. Annual cicadas require several years to develop, but generations overlap and some adults emerge each year. This annual visit contrasts with the massive synchronous appearance of the periodical cicadas that occur in specific geographic locations at intervals of 13 and 17 years, in the late spring and early summer.
When threatened by a predator or an entomologist, a male cicada produces the squawk call.
Another interesting difference between periodical and annual cicadas is their strategy for survival. Periodical cicadas rely on strength in numbers to overwhelm the capacity of predators to consume them. The emergence of ginormous numbers of periodical cicadas allows hungry predators to eat their fill, yet enough cicadas remain to successfully reproduce and carry on. The dog day cicadas rely on stealth and speed. It is unlikely that you will see, capture, or photograph a healthy dog day cicada in a treetop. Their green and black coloration creates camouflage, enabling them to blend into their arboreal environment. They have excellent eyesight and can fly like F-14’s. When you locate one and approach, keen eyesight allows them to spot you and rapidly fly away. Unfortunately for the dog day cicada, the cicada killer wasp we met in a previous episode has mastered the art of finding and capturing these marvelous insects.
Your best bet for getting up close and personal with a dog day cicada may be to wait until nightfall, grab a flashlight, head for your favorite cicada tree, and watch for the nymphs to arise from their subterranean crypts. With a hint of autumn beginning to creep into our nights, dog day cicadas will soon disappear. But on the remaining sunny days of what has been a spectacular summer for dog day cicadas, why not sit back with a cool drink and enjoy the chorus?
References
Information for this episode came from the excellent websites listed below. To learn more about dog day cicadas and their kin please visit these websites:
http://www.cicadamania.com/genera/
http://insects.ummz.lsa.umich.edu/fauna/Michigan_Cicadas/Michigan/Index.html