Liorhyssus hyalinus is a species of scentless plant bugs belonging to the family Rhopalidae, subfamily Rhopalinae.
Liorhyssus hyalinus can reach a length of 6.5–7.5 millimetres (0.26–0.30 in). The basic body color varies from yellow-brown to red, but the upperside of the abdomen is mainly dark. This species can be distinguished by the length of the hyaline membrane of the hemelytra, which extends beyond the black upperside of the abdomen. There are two black spots at the extremity of the pronotum. These bugs are rather similar to Rhopalus and Stictopleurus species.
Adults are present all year around. As the whole Rhopalidae family, this species a plant feeder. It mainly feeds on Compositae and Erodium species.