Sclerosomatidae are a widespread family of harvestmen (order Opiliones) known for their typically long legs and oval, single-sectioned bodies. They are often mistakenly called "spiders" or "daddy longlegs" but belong to a distinct order of arachnids.
Key Facts About Sclerosomatidae Harvestmen
Not Spiders: Harvestmen are arachnids, but they are not spiders. Unlike spiders, they have one fused body section (cephalothorax and abdomen are broadly joined), two eyes located on a raised bump (spiders typically have six to eight eyes), and lack venom glands and silk-producing spinnerets.
Harmless to Humans: The myth that they are highly venomous is false. They do not have fangs, their mouthparts (chelicerae) are too small to bite humans, and they pose no threat.
Sensory Legs: Their second pair of legs is often the longest and is used as highly sensitive "feelers" or antennae to sense the environment and detect prey.
Defense Mechanisms: When threatened, they can detach a leg, which will continue to twitch to distract the predator while the harvestman escapes. The lost leg does not grow back. They can also secrete foul-smelling chemicals to deter predators.
Diet: They are primarily omnivores and scavengers, using their mouthparts to ingest solid food chunks (unlike spiders which suck liquids). Their diet includes small insects, mites, aphids, fungi, plant fluids, feces, and carrion.
Habitat and Behavior: They are typically nocturnal and prefer damp, shady environments like leaf litter, under logs and rocks, and in basements or garages. Some species, such as those in the genus Leiobunum, are known to aggregate in large groups, possibly to conserve moisture.
Reproduction: Unlike most other arachnids, male harvestmen have a penis and engage in direct copulation to inseminate the female. In some species, males exhibit unusual parental care, guarding the eggs. Some species can even reproduce asexually through parthenogenesis.
Ancient Lineage: Harvestmen are an ancient order of animals, with fossils found dating back over 400 million years, existing long before dinosaurs.
