Papilio xuthus

Papilio xuthus, the Asian swallowtail, Chinese yellow swallowtail or Xuthus swallowtail, is a yellow-colored, medium to large sized swallowtail butterfly found in northeast Asia, northern Myanmar, southern China, Taiwan, the Korean Peninsula, Japan (from Hokkaidō to the Yaeyama Islands), Siberia and the Hawaiian Islands. It was also recorded in the state of Arunachal Pradesh, India, in 2014. It mates multiple times in its life, leading to an increased genetic diversity in its young. It is preyed upon by a host of organisms, including the tree cricket Oecanthus longicauda, ant Lasius niger, and wasps (Polistes and Trogus mactator). P. xuthus utilizes color vision and color constancy while foraging for plants of the family Rutaceae. It is common and not threatened. Papilio xuthus is common in urban, suburban, woods and orange orchards. The flight period is from May to August. Males use both physical and visual cues to attract mates during the breeding season. Females of the species regularly mate with multiple partners. After mating, females use habitat and food quality to determine where they will oviposit their eggs. Papilio xuthus is a member of the genus Papilio, of which Papilio appalachiensis, Papilio canadensis, and Papilio glaucus are also members. It is of the family Papilionidae and order Lepidoptera. It was first introduced in Hawaii in 1971 from Japan or Guam. P. xuthus makes significant seasonal migrations over 200 km. There are two subspecies of P. xuthus: Papilio xuthus koxingus and Papilio xuthus neoxuthus. The Asian swallowtail is a mid-sized, yellow, prominently-tailed butterfly. It has a wingspan of 45 to 55 mm. Its normal color pattern consists of a black pattern on a yellow background. Wing coloration is sexually dimorphic, with females showing broader proximal marginal bands in the hindwing. Blue-iridesecent and orange scales separate the black bands on the hindwing. The black bands also run in stripes of varying thickness along the forewing. The young caterpillar mimics bird feces and has a white and brown spot on its head. As they mature, caterpillars develop a light green body color with brown spots. P. xuthus have highly sensitive photoreceptors, or ommatidia, that can detect a wide range of wavelengths. This adaptation helps them identify members of their own species. Their distinct coloring and patterning are what sets them apart from other butterflies. Wing color is derived from “scales”, and P. xuthus has scales of yellow (cream), orange, black, and blue from the light each scale absorbs and reflects. Spectrophotometer studies saw that the yellow scales absorbed in the UV to violet range, orange absorbed in the lower half-wavelengths of the visible spectrum, black scales absorbed in most of the visible light range, and blue scales absorbed very little light. These absorbance ranges are due to the pigment molecules contained in each wing scale. Yellow and orange contain papiliochrome II and black contains melanin. The blue scales are unique in that they don’t have a pigment molecule, and are instead colored by an optical phenomenon. The interaction of light with the upper and lower lamina of the scale gives them the distinct blue color that we see. Experimental manipulation of wing coloration has been achieved through administration of the acid carboxypeptidase, Molsin. Injection of Molsin into 0-2 day pupae, butterflies had high amounts of black wing scales. These modified subjects had produced high amounts of melanin and papiliochrome II. Injection of Molsin into 3-4 day pupae shows no change in wing coloration. This indicates that P. xuthus likely has an acid carboxypeptidase of its own that naturally induces production of these pigments, and its action lasts during the first two days of pupation. Administration of a higher amount of acid carboxypeptidase to the pupae at 0-2 days induces an overproduction of pigmentation molecules, which leads to a high number of black scales.