Six families of the cryptic moth,Allophyes oxyucanthae, four of which contained both the typical and melanic forms of this polymorphic species, were tested for evidence of resting site selection in a large box lined with oak bark of three reflectances. Moths from different families were tested separately. Typicals from all four families tended to show a preference for the background which most closely matched their reflectance and on which they were most cryptic. Melanic moths from different families showed different resting site selection behaviour; those from two families preferring dark bark, on which melanics were most cryptic, while those from other families did not. The significance of these results in relation to previous suggestions about the control of resting site selection is discussed