Length about 7 mm. A striking orange-brown bug with long legs and antennae. The upperside is smooth and almost completely hairless. The rear of the corium is usually dark and the cuneus entirely orange. The tibial spines in this species are roughly equal to the tibial width. The closely related and similar M. beckeri has longer tibial spines and is found on Scots pine.

M. infusum is found on oak.

Adult: July to October.

Feeds on small insects as well as oak sap.

Fairly frequent across most of England and Wales.

Status in Leicestershire and Rutland not known.