Wikijunior:Bugs/Harvestman (Daddy Longlegs)

What does it look like?
Harvestmen are sometimes called Daddy longlegs. Other common names are granddaddy-longlegs, harvest spiders, shepherd spiders, and reapers.

They belong to the class Arachnida, but are not true spiders. Many different kinds of creatures belong to this class, including spiders, scorpions, mites, and ticks. Harvestmen are opilionids. The body is a single oval unit. There is no constriction between the cephalothorax and the abdomen. Unlike spiders, harvestmen do not have a segmented abdomen.

They have 2 eyes, often on raised structures. Chelicerae (pincers) have 3 segments; pedipalps (feelers) have 6 segments. The 4 pairs of walking legs have 7 segments. The second pair of legs is longest and acts like antennae. All of the legs are attached to the cephalothorax. None are attached to the abdomen.

Harvestmen have extremely long, thin legs. The legs break off easily and do not grow back. The reddish-brown body is 1/8 to 1/2 inch long. There is a very small claw at the tip of each pedipalp.

Worldwide, there are about forty families of Harvestmen. Only members of the Phalangiidae family—Eastern Daddy longlegs and Brown Daddy longlegs— are considered true Daddy longlegs.

Eastern Daddy longlegs are yellowish to greenish-brown. They are 1 /4 to 3/8 of an inch long. There is a blackish stripe on each side of the body. Their long thin legs are pale to dark colored.

Brown Daddy longlegs have a reddish-brown body. They are 1/8 to 1 /4 of an inch long with long dark legs.

Harvestmen in the Family Cosmetidae are generally dull-colored. Some are able to change color to blend in with their surroundings. Harvestmen in the tropics are green or yellow with reddish-brown legs.

Many Harvestmen in the Family Gonyleptidae are brightly colored. They usually have stout bodies with small bumps on the surface. The hind legs sometimes have long, sharp spines. Males tend to have smaller bodies, with more spines on their legs, than females.

The endangered Cokendolpher Cave Harvestman is small and does not have eyes. It is also known as Robber Baron Cave Harvestman.

Where does it live?
Most harvestman species live in moist, shady environments like caves, basements and deep woods. They are found under logs and rocks. Cosmetids live in tropical regions of North and South America. They are found under stones and debris in grassland, forest, and semidesert regions. Gonyleptids live in South American tropical forests, under logs and stones. Eastern Daddy longlegs are found east of the Rocky Mountains. They are found on leaves, tree trunks, and shady walls of buildings.

Brown Daddy longlegs are found throughout North America. They can be seen in shady areas and in fields. They hide under rocks, on tree trunks and foliage in open areas. Cokendolpher Cave Harvestmen are only found in Bexar County Texas. They are subterranean, living underground in a cave. Much of their habitat has been destroyed. None have been seen since 1993.

What does it eat?
Harvestmen are mostly scavengers. They are omnivores, feeding on insects and plants. In darkness, they search for slow-moving or dead insects. They eat small insects, insect eggs, mites, and earthworms. They eat fungi, decaying organic plant material and juices. Sometimes adults store food for their larvae to eat.

How does it defend itself?
Harvestmen are eaten by birds, large spiders, and predatory insects. They have spines on their legs to fend off predators. If a leg falls off, it keeps twitching a while. Scientists believe this helps detract predators so the harvestman can escape.

Harvestmen do not have venom glands. They have special glands on the carapace (protective covering). Crystals in these glands contain a defensive fluid with a distinctive odor. When attacked, the harvestman regurgitates a drop of fluid to mix with the crystals. The tips of the forelegs are dipped into the fluid then brushed onto the attacker. This defense is called “leg dabbing”. Some fluid remains on the harvestman’s body to keep the attacker away. The fluid is replenished when the harvestman drinks water.

What stages of metamorphosis does it go through?
Male Harvestmen do not court females before mating. Some species reproduce by direct fertilization. In a few species, females reproduce without males.

After fertilization, females use a special slender tube (ovipositor) to insert hundreds of eggs into cracks in the soil. The eggs are inserted one-by-one and overwinter in the soil. Females of one Gonyleptid species build a mud wall around their eggs to protect them.

Young harvestmen molt as they slowly grow larger in the soil. The outgrown cuticle is shed and replaced with a larger one. The new one has folded membranes inside. It is soft and fragile. The immature harvestman swallows air to swell up inside and expand the new cuticle. The mature harvestman will split the cuticle and crawl out in summer. One generation matures each year. In areas where frost occurs, few adults survive until spring.

What special behaviour does it exhibit?
Harvestmen have no silk glands, so they are unable to spin webs to catch prey. They hunt at night and will sit motionless on leaves waiting to ambush their prey.

Dozens of adult daddy longlegs often gather close together with their legs interlaced. In cold weather, they may cluster in knotholes of trees. In dry climates, they gather together during the day. Scientists think they do this to avoid drying out.

Some species of Harvestmen have red mites parasites attached to their legs.

How does this bug affect people?
Harvestmen rarely enter houses. They may be considered a nuisance when they gather in large numbers.

They are medically harmless to people. They do not harm animals, crops, or buildings. They are not venomous although many people wrongly think they are. Some people believe they do not bite. Others say the fangs are able to penetrate skin but only cause a mild reaction.

People once believed daddy longlegs could find lost cattle. To find a lost herd, a farmer would pick up a daddy longlegs by its legs. One leg was left free to point in the direction of the cattle. Some people think killing a daddy longlegs will bring rain.

Harvestmen are beneficial because they eat insects and help decompose dead organic matter.