KATYDID, the name given to certain North American insects, belonging to the family Locustidae, and related to the green or tree grasshoppers of England. As in other members of the family, the chirrup, alleged to resemble the words “Katydid,” is produced by the friction of a file on the underside of the left forewing over a ridge on the upperside of the right. Several species, belonging mostly to the genera Microcentonus and Cyrtophallus, are known.