BEHAVIOURAL ADAPTATIONS OF CRYPTIC MOTHS .3. RESTING ATTITUDES OF 2 BARK-LIKE SPECIES, MELANOLOPHIA-CANADARIA AND CATOCALA-ULTRONIA

Two bark-like moth species were tested for resting attitude preferences in an experimental apparatus which allowed a choice between backgrounds having vertically or horizontally oriented surface irregularities. The moths were exposed to either the tactile and visual clues associated with these backgrounds, or to the visual clues alone. When exposed to the tactile and visual stimuli of the backgrounds, a geometrid, with prominent transverse markings, rested at right angles to the surface irregularities (whatever their orientation). Under these same conditions, a noctuid, with prominent longitudinal markings, rested in a head-down attitude, and preferred the vertically oriented surface irregularities. When exposed to only the visual stimuli of these backgrounds, the geometrid exhibited a random distribution of resting attitudes which were unrelated to the background patterns. The noctuid under these conditions maintained its head-down attitude, but lost its preference for the vertically oriented background patterns. On the basis of these results, two mechanisms for effecting an alignment of moth and background patterns are proposed. © 1969.