Blue cicadas. Did you know they exist? They do… at least in Australia.
Then there is the Blue Moon blue colored morph of Cyclochila australasiae:
Photo by David Emery
Cyclochila australasiae come in many colors, but the most common color is green. “Blue Moon” is a good nickname for these cicadas because they are rare and only found, idiomatically speaking, “once in a Blue Moon”.
So, why are some cicadas blue, when their species is typically green? Here is a quote from the paper Blue, red, and yellow insects by B. G. BENNETT, Entomology Division, DSIR, Private Bag, Auckland, New Zealand:
The colours of insects are often due to a complex mixture of pigments, some of which
are concentrated from their diet. These are carotenoids, flavonoids, and anthraquinones, and some are porphyrins made from the breakdown of plant chlorophyll. Insectoverdin is a common green pigment produced by a mixture of blue and yellow compounds. The blue is tetrapyrrole, but sometimes an anthocyanin, and the yellow is a carotenoid.
Blue + yellow = green. If the yellow is missing, you get a blue cicada. I heard that, at least in the case of the Cyclochila australasiae, the blue cicadas are typically females. Perhaps something related to genetics or behavior of the females leads to an inability to process the caroteniods ingested along with their diet (tree fluids). I’m not sure, but it’s a topic that fascinates me, so I’ll continue to look into it.