You might try to sneak up close to see to see what’s making the noise, but these creatures are canny and see you coming first. They are well camouflaged and will go quiet until your back is turned again, and then the cacophony of sound resumes.
The noise is made by the males, trying to woo the ladies by rapidly vibrating drum-like plates called tymbals on their abdomens. The females make clicking sounds with their wings if they like the song, but it is unlikely to be just one couple, there will be hundreds making this incredible buzzing noise. it always sounds a bit like some sort of electrical buzzing to me, and I have no idea how they distinguish one from another!
They started their life as eggs, with a female laying 200-400 of them in tiny holes made in the branches of trees or shrubs. Six to ten weeks later, the young, called nymphs, hatch out and immediately fall to the ground, where they burrow underground and attach themselves to tree roots, where they feed by sucking the sap from the trees. They can stay there from one to 17 years apparently, depending on the species, and when this dormant period ends, they emerge above ground.
What sparks their emergence is what experts believe to be an internal clock, most likely put in motion by environmental cues that signify the passing of time, such as the trees coming into leaf and changing the composition of the fluid on which they feed. They go through five stages as nymphs, and it is likely the day of emergence is triggered by accumulated ground temperature.
They arrive above ground at sunset, climb the trunk of a nearby tree, and shed their skin to become adult cicadas, and so the cycle begins again. They start with the noise, they mate, lay their eggs, and then both males and females die after just about five weeks above ground.
Scientists have divided the over 3,000 cicada species into two groups: annual and periodical. Annual cicadas emerge from the ground at different times each summer. They’re usually dark with greenish markings, and they avoid being eaten by camouflaging themselves in the trees and flying from likely predators.
But it won’t be just one - there will be hundreds, but they aren’t harmful. They don’t attack people, they don’t bite or sting, and they don’t destroy crops, although female cicadas can damage the branches of young or newly planted trees when they lay eggs with their sharp ovipositors, or egg-laying tubes, and this can inhibit the trees' ability to bear fruit. The adult insect, known as an imago at its final stage, is quite big, 2 to 5 cm, long, with veined and transparent wings, and in some species have darker veins near the tips of the wings making the shape of a ‘W.’ They have no stingers and lack chewing mouthparts, so they can't bite you - they feed only on plant sap using their piercing, sucking mouthparts. They feed on a huge range of plants, including eucalyptus and grasses, and are preyed on by many different creatures - birds, bats, spiders, wasps, ants, mantids and crickets. They survive by having such a large population that predators couldn’t possibly eat them all.
And wow, they are loud - choruses of male cicadas can reach 80 to 100 decibels in volume! While no species of cicada is endangered, a few are at risk according to the International Union for Conservation of Nature (IUCN). The New Forest in the UK is where the only British species lives, but they haven’t been seen for around 10 years, so fall into the highly endangered category. The reasons could be many - reduction in habitat from animal grazing, increased bracken growth making it too cool and shady for them to survive, and of course our old culprit, climate change.
Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man.