Harvestmen are a common sight in gardens and homes, often recognized by their small, oval bodies and exceptionally long, slender legs. Understanding their true nature helps dispel common misconceptions and appreciate their role in ecosystems.
What Are Harvestmen?
Harvestmen belong to the order Opiliones, classifying them as arachnids. Most have one pair of eyes, usually located on a raised bump on their body, though some species are eyeless.
They are known for their long, thin legs; the second pair is often longer than the others and functions as sensory feelers to explore their surroundings. Harvestmen typically inhabit damp, dark places, such as under rocks, logs, or in leaf litter, and are often nocturnal. Their diet is quite varied, including small insects, decaying plant matter, fungi, and even dead animals, which they tear into small pieces with their mouthparts.
Are Harvestmen Venomous?
A widespread myth claims that harvestmen possess venom but cannot bite humans due to small fangs. Harvestmen are not venomous. They do not have venom glands or hollow fangs capable of injecting venom.
Their mouthparts, called chelicerae, are small, pincer-like structures used for grasping and tearing food, not for envenomation. These mouthparts are generally too small and not strong enough to break human skin. When disturbed, harvestmen employ various harmless defense mechanisms, such as releasing a foul-smelling fluid from scent glands, playing dead, or simply fleeing. Some can also detach a leg to distract a predator, a process known as autotomy.
Harvestmen vs. Spiders: A Common Confusion
Harvestmen are frequently mistaken for spiders, largely due to their eight legs and similar overall appearance. However, they are classified in a separate order, Opiliones, and are not true spiders. A primary distinguishing feature is their body structure: harvestmen have a single, fused body segment, giving them a more globular appearance. In contrast, spiders have two distinct body segments, a cephalothorax and an abdomen, joined by a narrow waist.
Harvestmen lack the ability to produce silk, meaning they do not spin webs for catching prey or for shelter. Most spiders, conversely, possess silk glands and use silk for various purposes. The absence of venom glands and fangs in harvestmen is another crucial difference, as nearly all spiders are venomous and use fangs to inject venom into their prey. This distinction highlights that harvestmen pose no threat to humans or pets.