Cerci always present; usually modified into unjointed forceps.
The Corixidae are small flattened water-bugs, with very short unjointed beak, the labrum being enclosed within the second From Marlatt, Bull.
The body is elongated and furnished with four pairs of short, unjointed, stump-like legs, each terminated by a pair of claws.
The first legs, meaning thereby the sixth pair of appendages, are generally pediform and locomotive, but sometimes unjointed, acting as a kind of brushes to cleanse the furca, while in the Polycopidae they are entirely wanting.
The tenth abdominal segment carries strong, unjointed cerci, while the presence of reproductive armature on the second abdominal segment of the male is a character found in no other order of the Hexapoda.