The creature behind the quintessential sound of summer is going to kick off Fauna Friday for a brand New Year: cicadas. Australia has over 200 species of cicadas, an insect with the enviable (?) title of being the loudest in the world – some calls can be as loud as 120 decibels (comparable to the average noise level of a chainsaw) and can cause pain to the human ear!
Cicadas produce their call by a complex mechanism of muscle contractions along a pair of ribbed membrane called tymbals located at the base of their abdomen. Each species has its own unique call and only male cicadas sing; primarily to attract females. Some species call in unison, climaxing their chorus into a crescendo that can become quite deafening; before diminishing in volume and repeating the repertoire. Researchers believe this communal singing serves to confuse potential predators (of which there are many: birds, bats, ants, spiders, mantids, wasps…) locating an individual, as well as the combined volume repelling some birds.
Cicadas spend the majority of their life underground in their larval stage as nymphs. The larvae of some Australian species can live underground for 6-7 years before emerging as an adult, shedding their tell-tale nymph skins (groovy zoological term: exuviae) on vertical structures, often tree trunks. Their adult stage is brief, usually only several weeks.
Cicadas are of the order Hemiptera, which include insects with piercing and sucking mouthparts such as aphids, scale insects and bugs. As underground nymphs, cicadas pierce and suck nutrients from plant roots. As adults, their mouth parts develop more elaborately into a sheathed structure (labium) containing four sharp stylets used for feeding. When not in use, their stylets are sheathed and folded back underneath almost their entire body length!
So next time you are feeling grumpy or put-out by a deafening cicada chorus, spare a thought for these critters who, in the space of a few short weeks, need to get used life above ground after so long in the soil (I think I’d be singing just to celebrate that fact alone!), attract a mate and breed all while trying not to get eaten!
The below photo is of an adult Green Grocer Cicada (Cyclochila australasiae) and shows clearly the two large compound eyes on the side of the head, as well as the three smaller central eyes on the dorsal surface of the head called ocelli (Photo credit: Skeeze from Pixabay). Other photo credits: Minscboo and Yukie Chen, Pixabay.