A widespread Palaearctic species, extending from the Pyrenees eastward to Siberia; in Europe it is generally distributed from France to Northern Italy, Romania and Ukraine, and extends far beyond the Arctic Circle in Scandinavia. It is very local and scarce throughout much of this range and probably more common in northern areas although it may be under-recorded because of its specialized lifestyle. The species is one of only two myrmecophilous members of the genus to occur in Europe, the other being M. conicicollis Chevrolat, with which it sometimes occurs. In the UK it is widespread though very local and rare in England and Wales; it was formerly more widespread, being also known from Ireland, but there seems to have been a general decline in recent times. Adults have been recorded from nests of Formica rufa Linnaeus, 1761, F. pratensis Retzius, F. aquilonia Yarrow, 1955, F. polyctena Förster, 1850, F. lugubris Zetterstedt, 1838, and F. exsecta Nylander, 1846. Little is known of the biology, but under laboratory conditions breeding has occurred in the spring, and both adults and larvae are thought to scavenge among detritus at the base of the nest; adults have been observed feeding on dead ants and frass. The species goes largely unnoticed by the ants and when detected the adults are mostly ignored, they are occasionally attacked but when this happens they retract their appendages into the body and remain motionless for long periods of time, during which their hosts eventually ignore them and move on. Adults occur year-round, they overwinter among debris within host nests and are active from March until October; they rarely leave the nest other than to mate and disperse in early spring. Recording generally requires searching through material taken from deep within nests, and nests built around the base of decaying trees is often most productive, but apart from spring dispersals when they may occur in large numbers, adults sometimes occur on bark or exposed wood on warm evenings near to nests.