Fig. 1. Experimental chambers warm the forest floor inhabited by ants in nest boxes.

(A) Geographic position of warming arrays at Duke Forest (orange) and Harvard Forest (green) toward the center and northern boundary of temperate deciduous forest (45) and the local spatial arrangement of the chambers at each site. Color intensity indicates greater MAT, with chamberless control plots indicated by unshaded symbols. (B) A single warming chamber at Duke Forest. Note that the diameter of each chamber is roughly 1000 ant body lengths. (C) Nest box containing a Crematogaster lineolata colony, with the cover tile removed.