Harvestmen Explained: How They Differ from Spiders, What They Eat and Whether They Are Dangerous

Are Harvestmen Actually Spiders?

No, harvestmen are not spiders. Although both belong to the class Arachnida, they are placed in different orders: spiders are in Araneae, while harvestmen are in Opiliones. You might know them as daddy longlegs, a common name that sometimes causes confusion with cellar spiders or crane flies. The key difference is body structure: spiders have two distinct body segments (cephalothorax and abdomen) separated by a narrow waist, while harvestmen have a single fused body segment that looks like an oval pill. Harvestmen also have only two eyes, often on a small raised turret, whereas most spiders have eight. On a quiet prairie walk, you can spot this difference with a close look—no need to disturb them.

Are Harvestmen Arachnids or Insects?

Harvestmen are arachnids, not insects. Both are arthropods, but arachnids have eight legs and two main body parts (or one fused part in harvestmen), while insects have six legs and three body parts. Harvestmen share the arachnid classification with spiders, scorpions, mites, and ticks. Unlike insects, they lack antennae and wings. Their eight long, thin legs are a giveaway, though sometimes a leg may be missing—harvestmen can detach a leg to escape predators, and the leg continues twitching. If you find one with seven legs, it is still a harvestman, not an insect.

Are Harvestmen Spiders Dangerous?

No, harvestmen are completely harmless to humans and pets. They do not have venom glands or fangs like spiders. Their mouthparts are small and designed for chewing soft food, not biting in defense. If you gently pick one up, it might use its front legs to investigate your skin, but it cannot break it. There is a persistent myth that harvestmen have the most potent venom but cannot bite—this is false. They have no venom at all. For birdwatchers, this means you can observe them closely without worry, though it is always best to let them go about their business undisturbed.

Why the Myth Persists

The confusion likely arises because cellar spiders (Pholcidae) are also called daddy longlegs, and they do have venom but are harmless to humans. Harvestmen, however, are a different group entirely. Their lack of venom is a key difference between spiders and harvestmen.

Difference Between Spiders and Harvestmen

Beyond body segments and venom, there are several observable differences. Harvestmen cannot spin silk or build webs; they have no silk glands. Spiders use silk for webs, egg sacs, and safety lines. Harvestmen also do not have the narrow waist typical of spiders. Their legs are exceptionally long and thin, and they can lose them without harm. In terms of vision, harvestmen rely more on touch and smell; their two eyes are simple. Spiders usually have eight eyes, though some have six or fewer. The table below summarizes these contrasts for quick reference in the field.

Harvestmen Arachnids: Identification in the Field

When you are out on the prairie, harvestmen are easy to recognize. Look for a small, roundish body no more than a quarter inch long, perched on eight thread-like legs that can span several inches. They often sit on leaves, fence posts, or the ground, sometimes gathering in groups. In late summer and fall, they are especially common, which is likely why they are called harvestmen—they appear around harvest time. Their body color ranges from brown to gray, often with a darker pattern. Unlike spiders, they do not move with sudden bursts; they walk steadily, using their second pair of legs like antennae to tap the surface ahead.

What Do Harvestmen Arachnids Eat?

Harvestmen are opportunistic omnivores. They eat small insects, mites, and other tiny invertebrates, but they also consume dead organic matter, plant juices, and fungi. Unlike spiders, they do not inject digestive fluids; they tear off small pieces with their chelicerae and chew them. If you watch one closely, you might see it pick at a dead fly or nibble a bit of overripe berry. Their feeding habits help clean up the prairie floor. For birdwatchers, harvestmen indicate a healthy ecosystem with plenty of microhabitats, which in turn supports insect-eating birds.

Observation Tip

On a dewy morning, check tall grasses for harvestmen feeding on small aphids or drinking water droplets. Use binoculars or a hand lens to avoid disturbing them. Keep a field notebook to record what they are eating—this can reveal the small invertebrate life that birds like sparrows depend on.

Seasonal Changes and Harvestmen Activity

Harvestmen are most visible from mid-summer to autumn. As the prairie cools, they may seek shelter under logs or leaf litter. You might find clusters of dozens of individuals huddled together, possibly to retain moisture. In winter, they are less active, but some species overwinter as eggs or adults in protected spots. Noting their presence over the seasons can enrich your field notes and help you anticipate what bird species might be around, as many birds supplement their diet with arachnids.

Respectful Observation for Birdwatchers

When you encounter harvestmen, observe them with the same respect you give birds. Avoid handling them roughly—legs detach easily, and while they can survive the loss, it is best not to cause it. Stay on designated paths to protect their microhabitats. If you lift a rock or log to look, gently replace it as you found it. Patient observation often reveals more than collection: watch how a harvestman uses its long legs to navigate stems, or how it reacts to a passing ant. These small dramas are part of the prairie's web of life, and noticing them deepens your connection to the birds that share the space.