I spotted this cicada empty cocoon case yesterday, and also happened to read the article by Kevin Short that has good info on cicads, posted here below.
NATURE IN SHORT / Summer great chance to learn about lilies, but best not pick any (The Yomiuri Shimbun)
Last week, I was exploring around some temples and shrines with my students, working up field notes on local folklore and sacred grove botany. When we pricked up our ears, we could hear a faint but distinct buzzing from high up in an elm tree. The first of the summer cicadas had already emerged from their underground burrows, and were getting an early start on their mating activities.
Cicadas lay their eggs on tree twigs from summer through early autumn. Their larvae soon hatch out and drop to the ground, where they quickly burrow into the soil. Cicada larvae feed by driving their long, strawlike mouthparts into the underground roots of trees. Depending on the species, they take from two to seven years to mature. (One U.S. species takes 17 years.) When they are ready, the final-stage larvae crawl out of the ground and climb up into the tree branches to metamorphose.
Most Japanese countryside cicadas prefer the hot, drier weather of full-blown summer to the cool, damp days of the monsoon. Ear-splitting cicada symphonies are a sure sign that high summer has begun. But every year a few impatient individuals seem to jump the gun. After a few days of “naka-yasumi” hot, summerlike weather that is frequently interspersed within the monsoon, the cicadas assume that the rains have broken and summer is here. Unfortunately, there’s no way a mistaken cicada can crawl back into his hole. Once he’s out, he’s out for good!