In her latest post, Jean Godawa writes about cicadas, whose mating call is one of the sounds we so closely associate with summer.
Labour Day has passed, signalling, for many, the end of summer. But the cicadas in the maple tree outside my window clearly don't follow the same calendar that I do. These insects that are usually associated with the dog days of summer, are still loudly buzzing away.
Cicadas are large, wide-bodied members of the true bug order Hemiptera, growing up to 5 cms (2 inches) long. The most common species in my area, the dog day cicadas (Neotibicen canicularis), certainly live up to their name, being active during the sultry days of July and August.
Despite their size, you are more likely to hear these large creatures than to see them; they spend most of their short adult lives high in the trees.
Using abdominal muscles and drum-like membranes called tymbals, male cicadas make noise to attract females for mating. The sound can be heard more than a kilometer away and can reach up to 120 decibels; that's louder than the sound produced by a motorcycle or power saw.
After mating, female cicadas lay eggs in small branches that die off and fall to the ground. The immature cicadas (nymphs) burrow into the ground and feed on plant roots for at least 2 to 5 years. We hear these loud insects every summer but the documented broods (numbered I through XIV) have predictable, staggered cycles, some as long as 17 years depending on the species.
Periodical cicadas (Magicicada spp.) have life spans of either 13 or 17 years. They are easily distinguished from other cicada species by their red eyes and reddish wing veins. Brood V emerged this year in the northeastern U.S. and the offspring of this brood won't be seen or heard until 2033. Brood VI will emerge next year in Georgia and the Carolinas. No data is available for the presence of periodical cicadas in Canada, while dog day cicadas, with much shorter life spans, are quite common in Ontario and Quebec.
|Carolina locust (Dissosteira carolina)|
Periodical cicadas have mistakenly been called 17 year locusts but are completely different from actual locusts, also known as grasshoppers (Orthoptera).
Large groups of cicada nymphs can cause serious damage to young tree roots and in an emerging year, thousands, if not millions of adults laying eggs can damage tree branches. In general though, cicadas are not considered an economically important pest, nor are they dangerous to humans.
When mature, cicada nymphs crawl out of the ground and onto tree trunks where they latch on and molt their exoskeleton to become winged adults.
You can often find these abandoned "shells", or exuviae, in early or mid-July on the ground or at the base of trees. You can see from these, the large, strong front legs that nymphs use to dig through the soil.
Adult cicadas use a straw shaped mouth to siphon sap from trees but they don't eat much and only live for a few weeks as adults, dying off with the summer.
While cicadas may munch on tree roots in our yards, some people advocate using large groups of cicadas to our advantage. They are, according to some scientists, a logical food choice for humans, since they belong to the same group of animals (Arthropods) as shrimp and lobsters. I admit that, in the interest of scientific curiosity, I have eaten insects. Most had kind of a nutty flavour. But I would much rather listen to the cicada song than have one for a snack. As long as I can hear them buzzing, I can be assured that summer is definitely not over yet.
About Jean Godawa: Jean is a science teacher and writer. She has been writing science-related articles for print and online publications for more than ten years. Jean holds a degree in biology and environmental science with a focus on entomology from the University of Toronto. She had conducted field research in the tropical rainforests of Asia and South America.
Many thanks again to photographer Ken Sproule and the wonderful people at bugwood.org for curating such an extensive catalogue of insect photographs.
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