The word Cicada derives from the Latin name for "tree cricket" (Cicada), but this is slightly poor nomenclature, as lots of people assume Cicadas to be related therefore to locusts, crickets and grasshoppers. Not so. Cicadas are in fact large BUGS (Hemipterans, although they do have their own suborder).
The males produce the incredibly loud, characteristic call but NOT by the process of "Stridulation" like grashoppers etc... (rubbing of body parts to produce noise).
Male Cicadas have "TIMBALS" at the sides of their abdominal base - complex pieces of membranes and thickened 'ribs' which are vibrated at incredibly high frequency using very strong muscles, against special resonance chambers in the abdomen, formed by specially adapted trachea. Got that? Its fair to say that if you watch a Cicada closely, with a view to see how they produce that incredible noise, you'll not have much luck.
The Cicadas were everywhere on Kephalonia - not much surprise really. Their Greek name is "TZITZIKIA". They are eaten in Greece (and all over the world for that matter), but unless you really want a bowl of Cicadas for your tea, watch how you pronounce your order of "TZATZIKI" (cucmber and garlic dip)!
There is one species of Cicada which lives in Britain, but you'll do well to hear or see them.
I've also posted ( in the post above) a couple of photographs sent to me by my (soon to be ) American Brother-In-Law, Trebus, who, in common with the rest of Chicago (and the mid west of the USA) have just had one of their "Cicada summers" - when millions upon millions of Cicadas hatch at one time (although I'm led to believe that this brood hatch was more impressive and numerous in the past), from a specific brood, after spending 17 years dormant underground. This particular brood is commonly known as BROOD XIII - sounds very evviiiiil doesn't it - and check out the eyes of the American Cicadas - almost glowing bright red!