Harvestmen, often recognized as “daddy longlegs,” are familiar sights in many homes and gardens. These long-legged creatures often cause confusion due to their resemblance to spiders. Many mistakenly believe they spin webs. This misunderstanding stems from their distinct biological differences from spiders.
Dispelling the Web Myth
Harvestmen (order Opiliones) do not construct webs because they lack the biological machinery for silk production. Unlike true spiders, harvestmen lack silk glands or spinnerets, the organs for extruding silk. Their body structure also differs from spiders. While spiders have two distinct body segments—a cephalothorax and a separate abdomen connected by a narrow waist—a harvestman’s cephalothorax and abdomen are broadly joined, making their body appear as a single, oval unit.
Harvestmen typically have two eyes, often on a raised tubercle, unlike most spiders with six to eight eyes. The popular “daddy longlegs” moniker also contributes to confusion with cellar spiders (family Pholcidae), which are true spiders that do spin webs and are often found indoors.
A Hunter’s Strategy
Without the ability to spin webs, harvestmen employ different methods to find and consume their food. They are primarily scavengers and opportunistic predators, relying on their long, slender legs as sensory tools to navigate their environment. The second pair of legs is particularly important, often held out in front of their bodies like antennae to detect vibrations and chemical cues from potential food sources. This adaptation allows them to explore their surroundings effectively, especially at night.
Harvestmen consume a diverse diet, including small, soft-bodied insects like aphids, mites, and beetle larvae. They also readily scavenge on decaying plant and animal matter, fungi, bird droppings, and even carrion, making them contributors to decomposition in their ecosystems. Unlike many spiders that use venom, harvestmen lack venom glands. They grasp and tear food with small, pincer-like mouthparts called chelicerae, ingesting solid particles rather than liquefied prey.
Harmless Neighbors
Despite their spider-like appearance, harvestmen are entirely harmless to humans. A common urban legend suggests they possess potent venom but cannot bite humans; however, harvestmen produce no venom. Their small chelicerae cannot pierce human skin, making a harmful bite impossible.
Harvestmen play a beneficial role in various ecosystems. By preying on small insects and insect eggs, they contribute to natural pest control in gardens and agricultural settings. Their scavenging habits, which include consuming decaying organic material, also make them valuable decomposers, helping to cycle nutrients back into the environment. These creatures are inhabitants of natural spaces, contributing to ecological balance without posing any threat to people.