Bug of the Month: Cicada
Written by Collin McMichael, Program Assistant
Just listen! There may be one or two left outdoors, but it is likely oddly quiet after the screeching cry of their love “songs” all summer.
Cicadas, also known as heat bugs though that is admittedly a new one for me, are nothing if not mildly infuriating at their peak. A few, specifically the dog-day cicadas, generally hang on until late summer and early fall. They are most active in the “dog days” of summer when Sirius is low on the horizon and, at least according to the Romans, is capable of causing fever and madness. In all honesty, I really was going to publish this earlier so it would catch the cicadas at their peak, but I am just going to blame the stars for this one since there are few things better than the pagan, stellar scape-dog.
Cicadas are insects in the order Hemiptera. Unlike most true-bugs, cicadas are in a special suborder called Auchenorrhynca which can probably land you a few points in Scrabble. The Auchenorrhynca, or neck-noses if you speak Greek since their proboscises appear to originate on the back of the head near the neck, used to make up a lot of their own order, the Homoptera. The Homoptera, unfortunately, happened to be paraphyletic. In other words, the Homopteran subgroups were incorrectly assumed to be the only groups derived from a single common ancestor when in fact it was the Hemipterans and the Homopterans who shared this great-great-so-many-greats-granddaddy. In the Homoptera, the cicadas, phylloxera, most bugs, and other similar beasties were quite content in their paraphyly, but then those pesky entomologists had to go and lump them in with the Hemipterans even though they have completely different looking wings. Regardless, Homoptera is no more. Long live Auchenorrhynca! And long do some of them live.
Cicadas probably have the longest lifespans of those-bugs-formerly-known-as-Homopterans. The shortest-lived cicadas can hang around for about two years. When you compare that to something like a housefly its close to 25 times the flies life expectancy! Of course, some cicadas live much longer than two years. The periodic cicadas here in the United States routinely live 13 or 17 years. They can almost legally vote! Interestingly, periodic cicadas always have lifespans that are prime numbers. It is hypothesized that this is evolution’s attempt to keep other animals from taking too much benefit from any frequently befalling buggy bonanzas.
As they start to swarm, cicadas can be quite numerous and rather hard to avoid. If you have ever gazed longingly into one of those shrieking demon’s eyes, I am sure you would have noticed their oddly striated, beak-like “nose”. This does not belie their relationship to the Hemipterans in favor of Arctic seabirds instead, it is the buccal pump I previously mentioned. Since cicadas feed on xylem sap, a substance analogous to water in that it is almost exactly water, they need this pump to suck their oh-so-nutritious vitals into their face hole. Xylem sap carries water and mineral up to the leaves from the roots, unlike phloem sap which carries sugars and other fun plant metabolites that most things would normally consider food around the plant wherever it is needed. Ridiculous calorie counters that they are, cicadas forgo this tasty, sugary substance that people often make into syrups in favor of the watery, low-energy schlock found in xylem root tissues, but, as a feast-or-famine adapted bipedal mammal, I might be biased. A cicadas preferred food source, or lack thereof, may well explain the long time periods associated with their development.
After a few years of doing what they can with as little as they are given, subterranean cicada nymphs will dig their way out of the ground. Itching for a release from their youthful trappings, nymphs crawl to the side of just about anything they can find and molt into their winged, adult form leaving behind crispy, brown shells that can easily be used to freak out your jumpier relations.
As with most insects, adulthood is where the fun begins. Once fully molted and ready to go, male cicadas will begin to vibrate their new tymbals, a membranous organ on the abdomen, to produce a high-pitched screech in an attempt to woo the ladies. Different cicadas produce different pitches and patterns of sound, and some are even loud enough to cause hearing impairment if you were to stand too close. For the lady cicadas, however, this screech is a siren’s song that they find wholly irresistible. Much about the cicada’s song remains elusive to us, but researchers do know that it is a duet. Females often respond with rustling wing flicks to signal receptiveness. Thankfully it doesn’t seem to be a case of the-loudest-male-wins or our descendants could need earplugs for picnics! By then though, the monsters from A Quiet Place would probably be a real and viable option as a biological control agent.
With any luck, cicadas will remain more of a quixotic totem and reliable staple to humans than an absolute menace. Cicadas have been an important food source for millennia. The youngish, recently eclosed adults tend to lack the chitinous crunch of the more mature variety, but all pack a punch of nutritious proteins and cholesterol free fats. Cicadas have been a feature in human culture and myth as well. Making an appearance in the Iliad along with showing up as a motif in Shang Dynasty art, cicadas have represented everything from lustfulness to immortality. So next time you find yourself unable to get any peace and quiet because of those dang bugs, just remember they are also cultural icons that should be appreciated or eaten, not cursed at!