go on periods of reduced monarch consumption. This cycle effectively reduces potential predation of monarchs by 50% and indicates that monarch aposematism has a legitimate purpose. The black-headed grosbeak has also evolved resistance mutations in the molecular target of the heart poisons, the sodium pump. The specific mutations that evolved in one of the grosbeak's four copies of the sodium pump gene are the same as those found in other milkweed butterflies like the common crow that also evolved to resist cardiac glycosides. Other bird predators include brown thrashers, grackles, robins, cardinals, sparrows, scrub jays, and pinyon jays. The monarch's white morph appeared in Oahu after the 1965–1966 introduction of two bulbul bird species, Pycnonotus cafer and Pycnonotus jocosus. These are now the most common avian insectivores in Hawaii, and probably the only ones that eat insects as large as monarchs. Although Hawaiian monarchs have low cardiac glycoside levels, the birds may also be tolerant of that toxin. The two species hunt the larvae and some pupae from the branches and undersides of leaves in milkweed bushes. The bulbuls also eat resting and ovipositing adults, but rarely flying ones. Because of its color, the white morph has a higher survival rate than the orange one. This is either because of apostatic selection (i.e., the birds have learned the orange monarchs can be eaten), because of camouflage (the white morph matches the white pubescence of milkweed or the patches of light shining through foliage), or because the white morph does not fit the bird's search image of a typical monarch, so is thus avoided. Some mice, particularly the black-eared mouse (Peromyscus melanotis), are, like all rodents, able to tolerate large doses of cardenolides and are able to eat monarchs. Overwintering adults become less toxic over time making them more vulnerable to predators. In Mexico, about 14% of the overwintering monarchs are eaten by birds and mice and black-eared mice can eat up to 40 monarchs per night. In North America, eggs and first-instar larvae of the monarch are eaten by larvae and adults of the introduced Asian lady beetle (Harmonia axyridis). The Chinese mantis (Tenodera sinensis) will consume the larvae once the gut is removed thus avoiding cardenolides. Predatory wasps commonly consume larvae, though large larvae may avoid wasp predation by dropping from the plant or by jerking their bodies. Aposematism Monarchs are toxic and foul-tasting because of the presence of