BUZZING OF RAIN?
As Arizonans wait to see how this year’s monsoon will play out, there is at least one encouraging sign, for those who believe in that sort of thing. Cicadas are buzzing.
Cicadas are the big, creepy yet harmless insects that put up quite a racket during the heat of summer. The loud buzzing sound of their mating call often gets noticed just before the start of monsoon rains, but that’s just a coincidence.
University of Arizona entomologist Gene Hall explains that the timing is more about the temperature than it is a forecast for rain.
“They’re generally out there when it’s the hottest, driest time of the summer, before the monsoon hits,” Hall said. “They do very well when it’s very hot and very dry and June is usually our hottest, driest time of the year here. The monsoon generally follows that period.”
Though cicadas are not weather forecasters, they are interesting insects. Following are a few more facts about the gentle giants.
What’s a cicada?
Cicadas are big, as bugs go. They can get to be about 2 inches long and about the thickness of an adult human thumb, but they don’t bite, sting or cause much damage.
They do make a lot of noise, though. Male cicadas make that distinctive buzzing sound by clicking a pair of thin, hardened membranes on the underside of their bodies to attract females. The sound gets louder as they try to drown
each other out to get the most attention.
Does Arizona have cicadas every year?
Unlike some parts of the country that get cicadas only in certain years – some species in the eastern United States mature just once every 17 years – Arizona is home to dozens of species of cicadas with different life cycles, so we see them every summer.
Cicadas live above ground for just the last few weeks of their lives. That time is used mainly for mating.
After mating, the females lay eggs in the bark of trees. Those eggs hatch, fall to the ground and burrow beneath the surface to feed on plant roots while maturing.
Most cicadas in this part of the country live underground for two to five years. When it’s time for them to surface they shed their juvenile skins and find a safe place to wait for their adult exoskeletons and wings to harden (usually overnight) so they can start the cycle all over again.
Why do they thrive in the heat?
The bugs are well adapted to survive in the heat by turning their bodies into sort of mini swamp coolers.
“They’re plant feeders and they have these piercing, sucking mouth parts that remove the juices from the plants,” Hall said. “They’re always taking in these liquids and in the heat their bodies can get overheated. So, what they do is they remove the water from their blood, then they cross that through pores on their exoskeleton. That allows a kind of evaporative cooling effect.”
Being able to cool themselves allows cicadas to be active during the hottest part of the day in the hottest part of the year. That works out well for them because many of their predators, such as birds and reptiles, aren’t active at that time.
What is a cicada killer wasp?
One predator that does hunt in the heat is the cicada killer wasp, a large, flying insect that would give cicadas nightmares if they could think.
Female cicada killer wasps fly around looking for cicadas. The wasp paralyzes the cicada with a sting and takes it to a burrow. The wasp then lays an egg on the cicada and buries it. The cicada stays alive underground while that egg hatches and the larva feeds off of its host, slowly killing it.
It sounds gruesome to us, but Hall said it’s just part of the life cycle.
“You have a natural predator going after its natural prey,” Hall said. “That’s been going on for a long time. The cicada killer wasp goes after cicadas, that’s just the way things are. The same thing with the fungus that attacks the nymphs when they’re underground.”
Hall was referring to a fungus that infects some cicadas while they are underground during their immature stage. This fungus infects their bodies, eventually kills them and then sprouts out of the dead cicada’s head.
Do cicadas bite? Are they harmful?
Cicadas don’t bite or carry diseases. And don’t worry if your dog eats one — they’re not poisonous. But they can cause problems for your pet if it eats a lot of them; they can be hard to digest.
“The only time I ever hear anybody complain about cicadas is generally from back East and the Midwest where the numbers are so large,” Hall said. “They’re out in such masses, the noise is just deafening.”
But the sound only lasts for a few weeks until the new brood of cicadas makes its way underground to mature.
“They’re completely harmless,” Hall said. “They’re just another wonderful part of the biodiversity in our region. They’re just neat, beautiful animals.”