Update: @Zi_kade on twitter (he’s a cicada expert in Japan) said that these deformities were caused by wind. Good news.
Radiation from the Fukushima reactor is possibly impacting cicadas in Japan. I say possibly, because I don’t know for sure, but the following articles infer that radiation is playing a part in cicada deformities and complications during eclosing (when they shed their nymph skins and become adults). Looks like about 20% of cicadas are affected in the study mentioned in the articles. It will be interesting to see how this story plays out. If the affected cicadas were in areas that flooded during the tsunami, it could be their bodies were damaged by water soaking the ground or flooding their tunnels.
Photos of possibly affected cicadas:
Use Google Translate http://translate.google.com/ if you can’t read Japanese.