hornworm
Rare term for a hornworm (a type of caterpillar). The cross-reference 青虫 (あおむし) suggests a related or more common word for caterpillar.
See also: 青虫
螟蛉 can be encountered in classical or specialized texts, but is hardly used in everyday life.
Archaic term for an adopted child. In modern Japanese, 養子 (ようし) is the standard word.
In old documents, examples can be found where 螟蛉 is used to mean an adopted child.