Hag Moth Facts: Their Caterpillar (Monkey Slug) Look Like a Hairy Spider

Have you ever heard of the hag moth caterpillar? This little-known creature may not be the most famous insect, but it certainly has some fascinating features, especially its camouflage ability. In this article, we’ll explore some fascinating facts about the hag moth and its larvae. 

Hag moth
Scientific name: Phobetron pithecium
Phylum: Chordata
Class: Insecta
Order: Lepidoptera
Family: Limacodidae
Genus: Phobetron

1. They are furry

The hag moth, a type of the slug caterpillar moth, is very hairy. They are covered in dense fur that extends from each leg. Both male and female moths have dark mottled brown wings, but males have translucent wings while females’ wings are slightly dull.

Another difference between the 2 genders is the size, with the females being bigger in size. Moreover, they possess light golden hair on their legs. This feature is missing in males. Their average wingspan is about 3 cm.

2. Habitat

Hag moths live in various habitats across the United States and Canada, including Florida, Mississippi, Maine Quebec, Arkansas, and Nebraska. You can rarely see the adult moths, but these species can be found in fields, forests, and woods during late spring through summer.

3. Their larvae look creepy

Compared to the adult, the hag moth caterpillar, with 2.5 cm, takes all the spotlight. Known as the monkey slug, these caterpillars possess a peculiar appearance.

Like their adults, the monkey slugs are covered in thick hair. This coat comes in different and bright color variants such as reddish-brown, white, tan, to black. Their abdomen is transparent, allowing you to see their open circulatory system, just like the glass frog. To know more details about this odd frog, you can follow our article here.

The hag moth larval features 9 pairs of hairy “arms” that coil around the body’s border. While 3 of the curly projecting appendages on each side are short, the other three are longer. Despite resembling legs, these extensions are not. Their true legs are located within their body.

The extra “arm” projections are capable of falling off without causing harm to the monkey slug. These arms provide providing additional protection, helping the larvae escape from predators if get caught.

Live in the Midwest Eastern and North America, hag moth caterpillars are skilled at camouflaging with their unusual look. Their brown coloring allows them to look like a dead leaf or the discarded skin of a hairy spider when stationary. When moving, their waving arms may lead them to be mistaken for a tarantula. Either way, they can protect themselves from birds.

The monkey slug hag moth caterpillar
If you see their underside, you can see their small legs and the clusters of white spikes hidden beneath the hair.

The underside of the monkey slug appears similar to a slug. You will see their suction cups, not their prolegs. These cups allow them to glide with a slug-like movement. Their true legs are near their head and under the thorax. These short legs are not used to move, but to grip objects.

Unlike other hairy caterpillars known for their spiky defenses, this particular species is non-poisonous and does not sting, according to what we read. However, you shouldn’t touch it for your own sake.

4. Diet

As adults, hag moths primarily feed on nectar from host plants such as apple, persimmon, oak, ash, birch, willow, chestnut, cherry, cedar, hickory, walnut, and dogwood. However, their larvae eat leaves from these trees.

Bats and wasps are the main predators of these moths. To defend themselves, they disguise themselves as their enemies. The male mimics a wasp, while the female mimics a bee, which can confuse and deter potential attackers.

5. Life cycle

Like all moth species, hag moths go through a reproductive cycle of 4 stages: eggs, larvae (caterpillar), pupa, and adult. Depending on the conditions, these creatures can generate multiple generations in a year.

During the breeding season, typically in spring, summer, or fall, the female hag moth lays a large number of small, transparent eggs. These eggs hatch into larvae. The main task of these caterpillars is to eat and molt. They go through several molts, during which they shed their skin four or five times and can increase in size up to 100 times their original size.

Next, the caterpillar enters the pupal stage. During this phase, it encases itself in a silken cocoon that resembles a cup and has a circular escape door. The cocoon dangles from trees or hides among the leaves.

Inside the cocoon, the monkey slug grows and develops arms, wings, legs, and other adult features. Finally, the adult hag moth emerges from the cocoon, ready to continue the life cycle.



Animal Facts 276

We are passionate animal enthusiasts with over a decade of experience studying animals. With a degree in zoology and conservation biology, we've contributed to various research and conservation projects. We're excited to bring you engaging content that highlights the wonders of the animal kingdom. We aim to inspire others to appreciate and protect wildlife through informative content grounded in expertise and passion. Join us as we delve into the captivating world of animals and discover the incredible stories they have to tell.

Leave a Comment