Fall webworm

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Fall webworm
Hyphantria cunea, adult.jpg
Scientific classification e
Kingdom: Animalia
Phylum: Euarthropoda
Class: Insecta
Order: Lepidoptera
Superfamily: Noctuoidea
Family: Erebidae
Genus: Hyphantria
Species: H. cunea
Binomial name
Hyphantria cunea
(Drury, 1773)
  • Phalaena cunea Drury, 1773
  • Phalaena liturata Goeze, 1781
  • Phalaena punctatissima Smith, 1797
  • Cycnia budea Hübner, 1823
  • Arctia textor Harris, 1823
  • Hyphantria textor Harris, 1841
  • Spilosoma mutans Walker, 1856
  • Hyphantria punctata Fitch, 1857
  • Hyphantria pallida Packard, 1864
  • Spilosoma candida Walker, [1865]
  • Hyphantria suffusa Strecker, 1900
  • Hyphantria brunnea Strecker, 1900

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 mainly an aesthetic pest and is not believed to harm otherwise healthy trees. It is well known to commercial tree services and arboriculturists.


The moth is native to North America, ranging from Canada to Mexico. It is one of the few insect pests introduced from North America into other continents. Introduced to what was formerly Yugoslavia in the 1940s (firstly recorded in 1949[1]), 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.[2] It spread into China, southern Mongolia, Korea and southern Primorsky Krai of Russia so that now it is considered holarctic in distribution.

Life cycle[edit]

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.[3]


The adult moth lays her eggs on the underside of leaves in 'hair'-covered clusters of a few hundred.[4] Eggs hatch in about a week.[5]


The caterpillars are highly variable in coloration, ranging from a pale yellow to dark grey, with yellow spots and long and short bristles.[3] 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.[5] The maximum length 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.[5]


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.[5]



The adult is mostly white in the north, but in the south it may be marked with black or brown spots on the forewings.[4][5] 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 of 35–42 mm.

Illustration of webworm (1917)

Food plants[edit]

Webworms moving in their nest.

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[6] and is considered to be among the most polyphagous of insects. In the eastern U.S., pecan, walnut, American elm, hickory, fruit trees, and some maples are preferred hosts; in some areas persimmon and sweetgum are also readily eaten. In the west, alder, willow, cottonwood and fruit trees are commonly used.[4]

Appearances in media[edit]

In the video game Metal Gear Solid 2: Sons of Liberty, the AI Colonel, while infected by a computer virus, mentions that he was a North American Fall Webworm in his past life and reminisces that "those were the good old days."


  1. ^ Lopez-Vaamonde, C.; Agassiz, D.; Augustin, S.; De Prins, J.; De Prins, W.; Gomboc, S.; Ivinskis, P.; Karsholt, O.; Koutroumpas, A.; Koutroumpa, F.; Laštůvka, Z. K.; Marabuto, E.; Olivella, E.; Przybylowicz, L.; Roques, A.; Ryrholm, N.; Sefrova, H.; Sima, P.; Sims, I.; Sinev, S.; Skulev, B.; Tomov, R.; Zilli, A.; Lees, D. (2010). "Lepidoptera. Chapter 11". BIORISK – Biodiversity and Ecosystem Risk Assessment. 4. doi:10.3897/biorisk.4.50. 
  2. ^ Gomi, Takeda (1996). "Changes in life-history traits of Fall Webworm within half a century of introduction into Japan.". Functional Ecology. 10: 384–389. doi:10.2307/2390287. 
  3. ^ a b Wagner, DL (2005). Caterpillars of Eastern Forests. Princeton, NJ: Princeton Univ. Press. 
  4. ^ a b c Douce, GK. "The Fall Webworm". Accessed August 21, 2006.
  5. ^ a b c d e Hyche, LL. "Fall webworm: A Guide to Recognition and Habits in Alabama". Accessed August 21, 2006.
  6. ^ Warren, LO; Tadic M (1970). The fall webworm, Hyphantria cunea (Drury). Arkansas Agric. Exp.Sta. Bull. 


External links[edit]