If you're looking for manga similar to Amrita no Kyouen, you might like these titles.
Socially-awkward Uehara has wanted to be an entomologist since he was a kid, and he spent all his time chasing that dream. When he failed, he was forced to come back to his home island, where his mother was completely unsympathetic to his problems. He arrived to his home island along with many other tourists, who were there to observe an unusual astronomical event. Afterward, Uehara encountered a strange bug whose bite transformed his body (including his penis). What is happening to Uehara, and what will become of his life?
They live under our feet... Sihwan Kim decides to stay at Dabin Park's house for a while. Little does he know that unidentified ants dwell below... Through an experiment, a monster-like ant creature is born and begins to kidnap people. Will Sihwan and Dabin, who are now caught up in the incident, be able to escape after twists and turns?
Sanpei is tranformed into a huge poisonous bug and seeks revenge on those who bullied and mistreated him as a boy.
A tunnel in a mountain that a college student visited with the intention of trying to deliver a video. The giant bugs that appeared there attacked them!
A dark romance story about a high school boy who falls helplessly in love with a beautiful girl who has to eat people to survive.
In the early 21st century, mankind is decimated when plants rise up, eating the populace and swallowing cities with their foliage. The remaining humans retreat underground in hopes of a safe haven, but nowhere is safe from the unspeakable horrors that want to hunt them down, and supplies are running thin...