Northern Two-Striped Walkingstick (Musk Mare)

Anisomorpha ferruginea

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Photo of mating pair of musk mares, on a gravel surface, viewed from above.
Musk mares have not historically been common in Missouri, but these were seen north of Boonville on November 2, 2013.
Other Common Name
Devil’s Riding Horse
Family

Pseudophasmatidae (striped walkingsticks) in the order Phasmida (walkingsticks)

Description

A tan, brown, or brownish-yellow, elongated insect lacking wings, resembling a short stick. Two-striped walkingsticks are chunkier than our other stick insects. They have 3 lengthwise stripes, though the side pair are often faint or diffuse; the stripe down the middle of the back is usually visible. The cerci (paired appendages at the tip of the abdomen) of females are short and stout. Females are much larger than males. Musk mares are usually seen as mating pairs, with the males riding on the backs of the females.

There are two species of musk mares in the southeast United States. The southern two-striped walkingstick (A. buprestoides) is not known from Missouri. It is a Gulf Coast species, ranging from Texas through Florida to South Carolina. It is larger, darker, and has 3 well-defined lengthwise black stripes. Its head is longer than it is wide. (The head of the northern species is about as long as it is wide, and the stripes on its body are much less distinct.)

Size

Length (excluding legs and antennae): 2 to 2¼ inches (females); 1 to 1½ inches (males).

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Photo of mating pair of musk mares on a mullein leaf.
Musk Mare Pair
During mating, the males look like miniature jockeys on horses as they ride atop the much larger females.

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Photo of mating pair of musk mares, plus another male, on a mullein leaf.
Musk Mare Trio
It is common to see many northern two-striped walkingsticks in a small area as they gather in fall for mating.

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Photo of a mating pair of musk mares, with the male not riding atop the female.
Musk Mares
Usually, the male rides on the female, but here, a disturbance must have caused the male to crawl off the female temporarily.
Habitat and conservation

Though they spend the summer eating and growing in trees and shrubs, musk mares are well camouflaged and rarely noticed. They are usually seen in the fall, when they congregate in open areas to mate. Then, they are usually seen in pairs on the ground or on low vegetation, in the copulating position they are famous for. Be careful: When they feel threatened or are handled, they can spray an irritating, acrid liquid for defense. If it contacts your eyes, it is said to burn like molten lead.

Foods

Like our more familiar walkingsticks, musk mares eat the leaves of trees and shrubs. Apparently they do not cause much noticeable damage to trees, at least in our area. They rely on their sticklike camouflage to hide them from predators, and if they are detected and attacked, they can spray an offensive, acrid fluid at their enemies.

image of Northern Two-Striped Walkingstick Musk Mare Devil's Riding Horse Distribution Map
Distribution in Missouri

Potentially statewide, but probably most common in the southern half of the state. Not historically common in Missouri, but reported in recent years from at least as north as the Missouri River. This species ranges from Texas and Kansas through Georgia and Virginia but is absent from Florida.

Status

Use great caution with these insects. When musk mares are pinched, poked, or otherwise feel threatened, they can squirt a smelly, milky, irritating fluid from glands just behind the head. They aim for the eyes, and their aim is amazingly accurate. In contact with eyes or other mucous membranes, it causes intense pain. If you’re squirted, flush your eye immediately with water. If you experience decreased vision, sensitivity to light, or other severe symptoms, seek medical attention.

Life cycle

Mating and egg laying occur in late summer and fall. Even when they’re not copulating, the small males ride the backs of the much larger females; because they look like miniature jockeys on horses, they acquired the common names “musk mare,” “devil rider,” and others. It can take several days for them to finish mating. Unlike other stick insects, female musk mares apparently deposit their eggs in the soil, instead of dropping them randomly from trees.

Human connections

The noxious spray of musk mares is well documented, so please use caution around these insects. It is best to simply leave them alone. There is a report of a dog suffering an ulcerated cornea after exposure to these chemicals, but that damage may have been self-inflicted in response to the pain.

Ecosystem connections

Musk mares help to limit the growth of vegetation. Over time, they help develop vigorous strains of plants that are least hindered by their leaf chomping. Although adult musk mares can repel predators with their spray, it is a safe bet that their eggs and young are devoured by many predators.