Changing altitude and habitat preferences of two species of wood-ant (Formica rufa and F. lugubris) in North Wales and Salop

SUMMARY 1 The distribution of two species of wood-ant in Mid and North Wales was investigated. 2 Formica rufa L. ranges from sea level to 200 m asl and is confined to warm sites with thermally favourable substrate open to direct insolation on south facing slopes. Most sites are on abandoned smelt furnace areas which provide stabilised islands of open ground surrounded by oak scrub. 3 Formica lugubris Zett. tolerates more shade, can survive on north facing slopes and is found at all altitudes to 305 m asl, the approximate treeline for the region. Populations still occur in natural open oak scrub at 200–300 m but the species has extended into derelict gold, copper and lead mine sites in wooded areas and has also spread into post-1920 conifer plantations. 4 Upland oakwood on boulder scree near Rhayader should be preserved as an example of natural high density F.lugubris populations. 5 The pattern of wood-ant distribution in England and Wales matches that of coppice distribution. This in turn reflects the history of pig iron production before the Industrial Revolution. Formica rufa, widespread in the primary iron producing region of S.E. England, is concentrated further north in the secondary iron producing areas of the Forest of Dean, Wyre, N.W. Wales and the Furness district of Cumbria and North Lancashire.