What Do Daddy Longlegs Eat? Harvestmen as Scavengers

A mixed diet of prey and scraps

Most arachnids, such as spiders and scorpions, are strict predators of live prey. Harvestmen, the order Opiliones, are different. Many species take almost anything small and nutritious they can find. Typical foods include:

• Small, soft-bodied insects such as aphids, springtails, small flies and caterpillars
• Mites, small worms, snails and slugs
• Insect eggs, including the eggs of moths
• Dead insects, spiders and other small animals
• Fungi, soft or rotting fruit and other plant matter
• Bird droppings and other animal waste

The balance between hunting and scavenging varies by species and season. The common harvestman, Phalangium opilio, is mainly a predator of soft-bodied animals in fields and gardens, such as aphids, caterpillars, leafhoppers, beetle larvae and mites, but it also scavenges dead insects. Some tropical harvestmen specialize in snails, while others in forest leaf litter live mostly on decaying material.

How harvestmen eat

A harvestman feeds with two pairs of front appendages. The chelicerae are small pincers that grab and tear food. Behind them, the pedipalps hold and turn the food, much like small arms. In some hunting species the pedipalps are spiny and help trap struggling prey.

The chelicerae shred food into small pieces and pass them to the mouth. This is a key difference from spiders, which inject digestive juices into prey and suck up the liquid. Harvestmen can take in small solid particles, which is one reason they can eat fungi, fruit and dead material that a spider would ignore.

After eating, a harvestman cleans its legs by drawing each one in turn through its mouthparts. Clean legs matter because they are covered in sense organs that the animal relies on to find its next meal.

How daddy longlegs find their food

Harvestmen have just one pair of simple eyes on a small bump on the back, and these eyes probably cannot form sharp images. Instead, harvestmen rely on touch and smell. The second pair of legs is the longest and works like a pair of antennae. As a harvestman walks, it taps the ground, leaves and stems ahead of it, and sensory hairs on these legs detect contact and chemical cues.

Most harvestmen feed at night. Some ambush prey, waiting until a small insect comes within reach, while others wander and pick up whatever they find. When an aphid colony or a dead insect is detected, the harvestman moves in and grabs it with its pedipalps and chelicerae.

Why harvestmen need water often

Harvestmen are prone to drying out. Their outer skeleton is thin, and many species lose water quickly in dry air. They drink often, from dew, raindrops, wet leaves and damp soil, and they tend to rest during the day in shaded, humid places such as under logs, in leaf litter or on the shady side of walls and tree trunks.

This need for moisture shapes when and where they feed. Activity is usually highest on warm, humid nights, and many species are most abundant near water or in damp woodland. Some species gather in large groups in sheltered places, which may help them save moisture as well as discourage predators.

Daddy longlegs in gardens and farmland

Because they eat aphids, caterpillars, mites and insect eggs, harvestmen are counted among the natural pest predators on farms. The common harvestman, for example, is known to eat the eggs of the corn earworm moth in soybean fields in North America. On its own it cannot control a pest outbreak, but together with spiders, ground beetles and ladybugs it helps keep plant-eating insects in check.

Harvestmen do not damage crops, homes or stored food. Although they nibble on soft or fallen fruit, they are not considered pests. Broad-spectrum insecticides kill them easily, so gardens with fewer chemicals usually have more of these helpful scavengers.

What do other “daddy longlegs” eat?

The name daddy longlegs is shared by two other animals, and their diets are quite different:

Cellar spiders are true spiders that catch prey in tangled webs and bite it with venom, then digest it into a liquid. They are known for catching other spiders, sometimes larger than themselves. For more on how true spiders feed, see what do spiders eat?. For the truth about the famous venom story, read are daddy longlegs venomous?.