Sunday, August 21, 2022

Dog Day Cicada Time


Dog day or annual cicadas are starting to get noisy outside. Males are singing to attract mates. There's more than one kind of annual cicada, with different species singing different songs and at different times of day or night. They sing with an organ called a timbal which is made of ribbed membranes that change shape with a click when pulled on by muscles. The clicks are amplified by hollow chambers in the insect. Click to enlarge. 

Here's a periodical cicada for comparison -- not what's singing now. These are the famous red-eyed ones that emerge in spring and early summer in 13 and 17 year cycles.
Some annual cicadas appear every year, but life cycles of individuals take from 2 to 5 years. They begin as eggs laid in slits on tree branches. (After the singing and mating is done.) The eggs hatch, nymphs fall to the ground and burrow down. They suck juices from plant roots, and eventually reach their last nymphal stage. Then they dig their way back up above ground, climb onto something and shed their skin and emerge as adults.

But here's a problem for dog day cicadas -- a big wasp known commonly as the "cicada killer."At about an inch and a half long, the cicada killer is one of our largest wasps. The huge size makes them look dangerous, but they are not aggressive -- except to cicadas.

When a female cicada killer is ready to lay eggs she digs a nest in the ground. (Lawns, planting beds, and the edges of concrete slabs are favorite sites.) Then she hunts for a cicada. She will sting it to paralyze it and then carry it to her nest. She'll push the cicada in and may go back to find another. After the nest is provisioned to her satisfaction she lays eggs on the paralyzed prey and seals the nest.

The eggs hatch into larvae that feed on the fresh cicadas their mother left for them. Then, plump and satisfied, the larvae become pupae and spend the winter underground. They dig upward to emerge from the nest the following summer. They fly around sipping flower nectar until the time comes to breed -- and to hunt cicadas. 

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