Fall webworm

The fall webworm (Hyphantria cunea) is a moth in the family Erebidae known principally for its larval stage, which creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods in the late summer and fall. It is considered a pest but does not harm otherwise healthy trees. It is well known to commercial tree services and arboriculturists. Fall webworms are an invasive species in East Asia.

The fall webworm (Hyphantria cunea) is a moth in the family Erebidae known principally for its larval stage, which creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods in the late summer and fall. It is considered a pest but does not harm otherwise healthy trees. It is well known to commercial tree services and arboriculturists. Fall webworms are an invasive species in East Asia. ==Distribution== The moth is native to North America, ranging from Canada to Mexico and has been introduced into other continents. Introduced to what was formerly Yugoslavia in the 1940s (firstly recorded in 1949 ), it now has occupied probably its entire range in Europe from France to the Caspian Sea in the east as well as penetrated into Central Asia: Turkmenistan (from 1990 to 1993), Uzbekistan (Fergana valley from 1996 to 1997), Kyrgyzstan, and southeastern Kazakhstan. It was also introduced into Japan in 1945 and has adjusted its number of generations per year since its arrival. It spread into China, southern Mongolia, Korea and southern Primorsky Krai of Russia so that now it is considered holarctic in distribution. ==Life cycle== One generation per year emerges in the northern part of North America, with larvae appearing in late summer through early fall. South of an approximate latitude of 40°N there are two or more generations annually, with webs appearing progressively earlier further south. The second generation is most damaging in southeast Pennsylvania and Delaware and emerges between 791 and 1540 growing degree-days. ===Eggs=== The adult moth lays her eggs on the underside of leaves in 'hair'-covered clusters of a few hundred. Eggs hatch in about a week. ===Larva=== The caterpillars are highly variable in coloration, ranging from a pale yellow to dark grey, with yellow spots and long and short bristles. There are two cream stripes along the sides. The two races—one more common in the north, the other in the south—differ in head capsule coloration. The maximum length of larvae is 35 mm. Webs are progressively enlarged and much messier looking than those of tent caterpillars (which occur only in spring and have shorter hairs and very little yellow on their bodies); also, webs from the fall webworm are concentrated to the tips of the branches, whereas the tent caterpillar webs are largely found in the unions. Larvae feed inside the tents until the late instars. Very young larvae feed only on the upper surfaces of leaves; later, they consume whole leaves. The larval stage lasts about four to six weeks. Larvae are known to wiggle vigorously at periodic intervals in synchrony. How they synchronize these movements especially when distributed over a wide area has not been established. ===Pupa=== The pupa stage overwinters in the bark and leaf litter at the base of the trees. It is dark brown and about 10 mm long. The thin brown cocoon is made of silk with bits of detritus interwoven. ===Adult=== The adult is mostly white in the North America regions, but in the south it may be marked with black or brown spots on the forewings. It is quite 'hairy' and the front legs have bright yellow or orange patches. The underwings will have less marking than the forewings, and the abdomen often has a sprinkling of brown hairs. It has a wingspan with a range of 35–42 mm. ==Food plants== The fall webworm feeds on just about any type of deciduous tree, where leaves are chewed; branches or the entire tree may become defoliated. Worldwide, it has been recorded from 636 species, and it is considered to be among the most polyphagous of insects. In the eastern U.S., pecan trees (Carya illinoinensis), black walnut, American elm (Ulmus americana L.), hickory, fruit trees, and some maples are preferred hosts; in some areas persimmon and sweetgum are also readily eaten. In the west, alder, willow (Salix spp.), cottonwood and fruit trees are commonly used. Additional host plant examples include madrone (Arbutus menziesii Pursh), mulberry, ailanthus, American sycamore (Platanus occidentalis L.), and Asian white birch (Betula platyphylla). Host plant selection is dependent on factors like the plant's degree of sun exposure, age, environmental stress undergone, toughness, and nutritional quality. For example, for an insect that needs energy for processes like dispersal or diapause, consuming plants that provide a lot of carbohydrates could be beneficial; for a female insect that is producing eggs, consuming plants that provide a lot of protein could be beneficial. Image:Hyphantria.JPG | Late instar larva Image:Hypahntria web.JPG | Web on willow Image:Hyphantria_cunea_damage_on_Acer_negundo.JPG | Damage on Acer negundo ==References== ==Further reading== Bat Man, 2003. The fall webworm. https://web.archive.org/web/20130613053245/http://www.bugwood.org/factsheets/webworm.html . Accessed Aug 21, 2006. Hyche, LL, 1999. Fall webworm: A guide to recognition and habits in Alabama. http://www.ag.auburn.edu/enpl/bulletins/fallwebworm/fallwebworm.htm Accessed August 21, 2006. Wagner, DL. 2005. Caterpillars of eastern forests. Princeton Univ. Press. Warren, LO and M Tadic. 1970. The fall webworm, Hyphantria cunea (Drury). Arkansas Agricultural Experiment Station Bulletin 759: 1–106. ==External links== Fall webworm on UKmoths Bagworm, Fall Webworm or Eastern Tent Caterpillar? August 18, 2001. Sandra Mason, University of Illinois Extension. Accessed May 31, 2010. U. Mass site U. Georgia site Ohio State U. site Texas A&M site Fall webworm on the UF / IFAS Featured Creatures website

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