Many of its component species are referred to as "tussock moths" of one sort or another. The caterpillar, or larval, stage of these species often has a distinctive appearance of alternating bristles and haired projections. Many tussock moth caterpillars have urticating hairs (often hidden among longer, softer hairs), which can cause painful reactions if they come into contact with skin.
Adult moths of this subfamily do not feed. They usually have muted colours (browns and greys), although some are white, and tend to be very hairy. Some females are flightless, and some have reduced wings. Usually, the females have a large tuft at the end of the abdomen. The males, at least, have tympanal organs. They are mostly nocturnal, but Schaefer lists 20 confirmed diurnal species and 20 more likely diurnal species (based on reduced eye size).
The larvae are also hairy, often with hairs packed in tufts, and in many species the hairs break off very easily and are extremely irritating to the skin (especially members of the genus Euproctis). This highly effective defence serves the moth throughout its life cycle. The hairs are incorporated into the cocoon. An emerging adult female of some species collects and stores the hairs at the tip of the abdomen and uses them to camouflage and protect the eggs as they are laid. In other species, the eggs are covered by a froth that soon hardens or are camouflaged by material the female collects and sticks to them. In the larvae of some species, hairs are gathered in dense tufts along the back and this gives them the common name of tussocks or tussock moths.
Lymantria means "destroyer", and several species are important defoliators of forest trees, including the spongy moth Lymantria dispar, the Douglas-fir tussock moth Orgyia pseudotsugata, and the nun moth Lymantria monacha. They tend to have broader host plant ranges than most Lepidoptera. Most feed on trees and shrubs, but some are known from vines, herbs, grasses, and lichens.
Taxonomy is a dynamic discipline, and recent phylogenetic studies have reclassified the family Lymantriidae as the subfamily Lymantriinae of the newly formed family Erebidae. The studies found that the family Lymantriidae form a specialized lineage within the Erebidae and is part of a clade that includes the litter moths (Herminiinae), the Aganainae, and the tiger and lichen moths (Arctiinae). The reclassification affected the former family as a whole and largely kept the clade intact.
In The God of Small Things by Arundhati Roy, the character Pappachi discovers a new species of lymantriid with "unusually dense dorsal tufts". At first, his discovery is misclassified as a race of an existing species. After Pappachi retires from the post of imperial entomologist, a taxonomic revision makes his moth the type species of a new genus. Pappachi's original claim is forgotten and the new genus is named for a former subordinate. The disappointment embitters Pappachi:
Hickory tussocks are native insects and are found every year, usually in small numbers. Occasionally the numbers will increase to where they are noticed by the general public. The caterpillars are showy and active during the day so they seem like just the cutest thing to play with. Unfortunately their hairy bodies can cause a rash in sensitive individuals.
Heavy localized populations of white-marked tussock moth (Orgyia leucostigma) caterpillars are being reported in central and western Ohio. Curtis Young (OSU Extension, Van Wert County) showed images during this week's BYGL Zoom Inservice of caterpillars on a variety of hosts including rose and noted he had received reports of hot spots in Allen, Hancock, and Putnam Counties. I received a report from Franklin County of 100% defoliation of a landscape redbud.
Although this native moth has the potential to produce widespread outbreaks in Ohio, the reports we've received thus far this season fit with its usual behavior. Most often high populations are extremely localized; sometimes confined to a single landscape. Such outbreaks are almost invariably single-season events with no repeat performances the following season.
Thankfully, there are many natural enemies of this native moth including predators, parasitoids, and pathogens. Indeed, there is a naturally occurring strain of nucleopolyhedrovirus that is specific to white-marked tussock caterpillars and is known to cause rapid collapses of outbreak populations including first-generation caterpillars.
Like other tussock moths (family Erebidae, subfamily Lymantriinae), white-marked tussock moth caterpillars have urticating hairs (stinging hairs). The hairs are not attached to venom glands like the hairs and bristles on more dangerous caterpillars. However, they can puncture the skin causing hives and skin rashes on individuals who are highly sensitive to the irritation.
Although white-marked tussock moth caterpillars are distinctive in their markings and coloration, other tussocks may be mistaken for them or vice versa. The caterpillars of the definite tussock moth (Orgyia definite) (I love the common name!) are often confused with white-marked tussock moth caterpillars. Their body plans are very similar; however, definite tussock moth caterpillars are definitely yellow. The caterpillars prefer willow but may also be found on oak, maple, hackberry, and birch.
Large numbers of caterpillars feed on fir tree needles, sometimes defoliating trees. They may fall from the tree canopy of firs and land on anything below, including people. Caterpillars will finish their feeding cycle and remain dormant until the following year, when they typically resurface in June. It is likely that they will be present in much greater numbers in 2021. Tussock moths can kill trees. However, it is possible for adult trees that have been defoliated up to 80% percent to still survive. Smaller seedlings and sapling often do not always recover as easily.
The parks work with entomologists from Region 5 of the U.S. Forest Service to monitor Douglas-fir tussock moth prevalence and will update this page as more information becomes available. The April 2020 Douglas-fir tussock moth leaflet includes more detailed information about the species, photos, and a list of references.
Rusty tussock caterpillars hatch from overwintering eggs in early spring. Caterpillars pupate in silk cocoons spun onto the undersides of branches in August. Several weeks following pupation, adult moths emerge. Male moths have wings that are rusty brown in color with each forewing bearing a small white marking. Male moths also possess plumose antennae, which are covered with microscopic chemosensors that enable the male moths to detect the pheromones of their female counterparts. The adult female moths are wingless, sedentary, and generally 12mm long. Adult females emit pheromones to attract the flighted males in order to mate. Females deposit eggs on the host plant on which she is currently residing, which is where they will overwinter until they hatch the following spring. There is only one generation per year.
DFTM has one generation per year. It overwinters as eggs. The eggs begin to hatch in late May at the time new foliage emerges. Early instars begin feeding on the young tips of the trees, usually near the top of the trees. As the larvae grow they begin to feed on older needles. Larvae can be wind dispersed as they hang from silk. The larvae pupate starting in late-July. Female moths are wingless and can be found on the tree near where they emerge from the pupal case. Males are attracted to the females through pheromones. Adults die at the end of the season.
The whitemarked tussock moth, Orgyia leucostigma, is a native insect that for unknown reasons, may suddenly become locally abundant. This insect overwinters as eggs in a mass laid in or on the mother's cocoon. In spring, the eggs hatch and the tiny, hairy caterpillars begin to feed and grow. Some drop from trees suspended by a silk strand. These may balloon for a considerable distance to invade new landscapes. After feeding for several weeks, the caterpillars eventually grow 1 to 11/2 inches long. They have two hair "pencils" of black setae that extend forward beyond the head and a rear "pencil" of black setae at the rear. The caterpillars also have four dense white clumps of short setae on the top of the first four abdominal segments as well as two bright red bumps on segments six and seven. Some of these setae contain urticating material that can cause dermatitis on sensitive skin. When mature, the caterpillars spin grayish cocoons inside of which they pupate. Cocoons are often abundant on bark and objects nearby. Sometime whitemarked tussock moth caterpillars can be a nuisance as they crawl about looking for a suitable place to spin their cocoons. About two weeks later, the moths emerge and mate. Male moths have mottled brown to brownish gray wings that have a purplish tint when newly emerged. Females have wings that are so short the moths appear to be wingless and are gray, plump creatures that lay their eggs in a mass on the cocoon and then cover the eggs with a frothy material that hardens into a protective covering. We have two generations per year in North Carolina.
Oak appears to be a favorite host in North Carolina as well as cherry, hackberry, and willow. However, whitemarked tussock moth caterpillars have been reported from plants in 116 genera. Dermatitis due to the urticating setae of tussock moth caterpillars has been reported from day-care centers and elementary schools when children play with these attractive caterpillars. Contact with the cocoons can produce the same symptoms even after cocoons are a year old.
Whitemarked tussock moth caterpillars are plagued with diseases, parasites, and predators, which may explain why they are seldom wide spread pests. By the time the caterpillars are usually noticed, they have probably finished feeding and are seeking a site to spin their cocoons. Applying a pesticide to mature, migrating caterpillars is a waste of time as they are quite tolerant of pesticides. The best time to spray is when the caterpillars are young and actively feeding. At that time even Bacillus thuringiensis formulations can give adequate control. Young caterpillars are also susceptible to pyrethroid insecticides available at most garden centers. However, it can be a challenge to safely get an insecticide up into the canopy of tall trees. Consider using the services of a professional landscaper or arborist for treating large trees. 781b155fdc