taking up resting positions in both males (Mikkola, 1979; 1984) and females (Liebert and Brakefield, 1987). Majerus, et al., (2000) have shown that peppered moths are cryptically camouflaged against their backgrounds when they rest in the boughs of trees. It is clear that in human visible wavelengths, typica are camouflaged against lichens and carbonaria against plain bark. However, birds are capable of seeing ultraviolet light that humans cannot see. Using an ultraviolet-sensitive video camera, Majerus et al. showed that typica reflect ultraviolet light in a speckled fashion and are camouflaged against crustose lichens common on branches, both in ultraviolet and human-visible wavelengths. However, typica are not as well camouflaged against foliose lichens common on tree trunks; though they are camouflaged in human wavelengths, in ultraviolet wavelengths, foliose lichens do not reflect ultraviolet light. During an experiment in Cambridge over the seven years 2001–2007 Majerus noted the natural resting positions of peppered moths, and of the 135 moths examined over half were on tree branches, mostly on the lower half of the branch, 37% were on tree trunks, mostly on the north side, and only 12.6% were resting on or under twigs. Polymorphism Introduction on forms There are several melanic and non-melanic morphs of the peppered moth. These are controlled genetically. A particular colour morph can be indicated in a standard way by following the species name in the form "morpha morph name". The use of "form" in the method of Biston betularia f. formname in detailing these variations is also a widespread practice. These forms are often accidentally elevated to subspecies status when they appear in literature. Not adding the "f." (forma) or morpha implies that the taxon is a subspecies instead of a form, as in Biston betularia carbonaria instead of Biston betularia f. carbonaria. Rarely, forms have been elevated to species status, as in Biston carbonaria. Either of these two circumstances might lead to the erroneous belief that speciation was involved in the observed evolution of the peppered moth. This is not the case; individuals of each morph interbreed and produce fertile offspring with individuals of all other morphs; hence there is only one peppered moth species. By contrast, different subspecies of the same species can theoretically interbreed with one another and will produce fully fertile and healthy offspring, but in practice do not, as they live in different regions or reproduce in different seasons. Full-fledged species are