“We see many cicadas walking around without their abdomen,” wrote University of Maryland entomology professor Paula M. Shrewsbury in an email. “The abdomen houses the organs of digestion and reproduction. The thorax is the center for musculature for locomotion (legs and wings). The head maintains sensory function. Because the head and thorax remain intact, the insect can still sense and respond to stimuli, orient and move despite the loss of the abdomen. That is why we see cicadas without abdomens walking around.”
“Their instinct, which is still intact, still drives them to mate. I think two (cicadas) are going to be disappointed in that relationship.”
And how long can cicadas live missing significant portions of their bodies?
“[I]t may be that they can live for a few weeks in this state. I’ve seen (impacted) individuals still active for a while, though seemingly more impaired,” wrote Daniel Gruner, also a professor in U-Md.’s entomology department.
The Massospora fungus, he continued, “effectively causes their ‘butt’ to fall off, which is then replaced by a plug of spores, and they continue to attempt to reproduce as if they are still capable, thus spreading the spores. The nymph emerges infected after encountering resting stages of the fungus in the soil, and just the last few segments later fall off to expose the spore plug.”
In the two videos of cicadas with missing body parts displayed in this article, above (which I recorded) and below (which he filmed), Gruner actually believes the cause was predators, rather than the fungus.
“The abdomens are simply missing,” he wrote. “Looks like choosy predators to me. After all, the predators have their choice of delectables, why eat the nasty parts?”
Correction: The original version of this story quoted University of Maryland entomology professor Daniel Gruner stating “adults do not feed and have no nutritional demands until they die" in describing how cicadas can survive without large parts of their bodies. He later was informed by a colleague that periodical cicadas can and do feed as adults. The statement about them not feeding was removed.