My favorite butterfly book, “Butterflies of the East Coast” by Rich Cech and Guy Tudor, says tails on a swallowtail’s wings “create directed airflows over the wings that enable extended glides at high angles – angles greater than those at which a butterfly with such broadly cut wings normally would stall.” Other researchers have found this to be true. The tails also help these strong fliers aerodynamically. This illusion is helped in several species by a false red eye spot with a black pupil-like spot. The tails appear to serve as a decoy, making birds and other predators attack the wrong end of the butterfly. I must say something about the tails that are the distinguishing feature of these creatures. The other dark swallowtails mimic pipevine swallowtails and gain some protection from looking like their poisonous cousins. Spicebush and black swallowtails both have two rows of orange spots, and dark female eastern tiger swallowtails have a row of crescent-shaped orange spots on the margin of each hind wing. The bottom side of the hind wings has a single curved line of round, orange spots positioned away from the wing’s margin. The dark swallowtail is mostly black above with a marvelous blue iridescence on the hind wing (more prominent in males). But they also will eat some foreign members of the family, including garden rue and hardy trifoliate orange, which some people grow as an ornamental plant even though the green fruits are inedible. Members of that plant family that are native to Pennsylvania are prickly ash (Zanthophyllum americanum) and wafer-ash, aka common hop-tree (Ptelea trifoliata). The female giant will only lay eggs on plants in the citrus family, the caterpillar’s sole food. This species is very large, but some female eastern tiger swallowtails have a greater wingspread. The undersides of the wings are mostly light yellow. Giant swallowtails are big and black with bands of bright yellow spots that make an X near the tip of each forewing when seen from above.
But some fruit growers also plant them, and the zebras sometimes find them. Pawpaws are found in a few places in Berks County, such as Nolde Forest, and they are also common along the lower Susquehanna River. The females lay their eggs on pawpaw tree leaves, and that is all the caterpillars will eat. The zebra swallowtail is small compared to its local relatives, but the long tails, especially long in individuals of the summer brood, are very elegant. Occasionally, the white parts of their wings have a beautiful turquoise cast that makes a freshly emerged individual a sight to behold. Zebra swallowtails have an unmistakable black and white stripe pattern and one red stripe on the underside of their hind wings. It sounds like what we talk about, doesn’t it? Diets and the weather.
They are uncommon for several reasons: food and winter weather. They are not seen nearly as often as the eastern tiger, black or spicebush swallowtails. Zebra, giants and pipevines are the three uncommon swallowtail species in this area.
0 kommentar(er)
