Friday, May 20, 2011

Western Tiger Swallowtail


Western Tiger Swallowtail
Adult Western Tiger Swallowtail  have a two-and-three-quarter to four-inch (seven- to ten-centimeter) wingspan. The wings are black and pale yellow with black tiger-stripes. The hindwings have tails at their lower tips that resemble the long tail feathers of a swallow; hence, their common name swallowtail. Also on the hindwing, there are narrow yellow spots along the wing's margin and orange tint on two spots near the end of the inner margin of the wing. Blue spots are found around the outer margin of the hindwing. The upper side of the hindwing may have a yellow spot on the outer margin. On the forewing, yellow spots form a continuous band along the outer margin of the wing. These yellow spots are bordered in black.

The Western Tiger Swallowtail (Papilio rutulus) is a common swallowtail butterfly of western North America, frequently seen in urban parks and gardens as well as in rural woodlands and riparian areas. It is a large, brightly colored and active butterfly, rarely seen at rest; its wingspan is 7 to 10 cm, and its wings are yellow with black stripes, and in addition it has blue and orange spots near its tail. It has the "tails" on the hind wings that are often found in swallowtails.

Western Tiger Swallowtail
A deep green, shiny, spherical egg is laid on the underside of a leaf. Eggs are laid singly, but there may be a number of them on the leaf. The caterpillars of Western Tiger Swallowtail, reach about two inches in length, are deep to light green in color, are swollen in the front, and have large yellow eyespots with black and blue pupils. There is a colored forked organ called the osmeterium located behind the head on the back of the caterpillar. This foul-smelling organ can turn inside out, and, along with the eyespots, may deter predators. The dark brown chrysalis overwinters slung from a twig or tree trunk. The chysalis is woodlike.


Western Tiger SwallowtailSwallowtail females may lay up to four batches of eggs in a season and up to one hundred eggs in total. The length of time that it takes for the larvae to emerge from the egg depends upon the weather, but generally, in summer, it takes four days. The larvae molt five times - called instars - before they pupate. After each molt, the caterpillar eats the old skin which is rich in nutrients.

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