The harvestman is a common, yet frequently misunderstood, member of the Class Arachnida, which also includes spiders, scorpions, and mites. Often seen in gardens and on shaded walls, this creature is recognizable by its small, oval body and eight disproportionately long, slender legs. Despite its familiar appearance, the harvestman belongs to a distinct group of arachnids known by the scientific order Opiliones. This ancient order represents a unique evolutionary path separate from its spider relatives.
Classification and Defining Features
The harvestman is classified within the Order Opiliones, an entirely separate taxonomic group from the Order Araneae, which contains all true spiders. This distinction is apparent in the fundamental structure of its body. A true spider possesses two body segments—a cephalothorax and an abdomen—connected by a narrow waist. In contrast, the harvestman’s body segments are broadly joined, or fused, creating the appearance of a single, oval-shaped unit. This feature is the most reliable way to differentiate a harvestman from a spider.
Harvestmen possess a unique visual apparatus, typically having only two simple eyes mounted on a raised structure called an ocularium. This contrasts with most spiders, which generally have six or eight eyes positioned around the margins of their cephalothorax.
Their eight legs are used for locomotion and serve a major sensory function. The second pair of legs is often the longest and is primarily used as feelers, constantly tapping the environment to detect vibrations and chemical cues. Harvestmen completely lack the specialized silk-producing glands that spiders use to construct webs, sacs, and draglines. Their chelicerae, or mouthparts, are small, pincer-like structures used for grasping and tearing food, rather than the venom-injecting fangs found in spiders.
Clearing Up Common Misconceptions
The harvestman suffers from a widespread identity crisis primarily because of the common name “Daddy Long Legs.” This vernacular term is applied to three different, unrelated creatures, causing significant public confusion. The name refers to the harvestman (Order Opiliones), the cellar spider (Family Pholcidae), and the crane fly (Order Diptera).
The cellar spider, although visually similar due to its long legs, is a true spider (Order Araneae) that produces silk and builds webs. The crane fly is a non-biting insect that resembles a giant mosquito and is not an arachnid at all. The harvestman is often mistakenly called a spider, but its fused body segments and inability to spin silk place it outside the spider classification.
The harvestman’s taxonomic separation is further confirmed by its digestive system. Unlike spiders, which typically liquefy their prey externally and suck the fluid, harvestmen are capable of ingesting small, solid particles of food.
Diet and Ecological Role
Harvestmen exhibit a broad and varied diet, classifying them as omnivores and scavengers, a trait unusual among arachnids. They consume a wide assortment of organic material, including small, soft-bodied insects, mites, plant matter, fungi, dead organisms, and bird droppings.
Their feeding habits contribute positively to local ecosystems, making them beneficial members of the garden environment. By consuming pest species like aphids and small caterpillars, they help regulate local arthropod populations. They also act as decomposers, assisting in the natural recycling of nutrients back into the soil.
Safety and Interaction with Humans
A common concern relates to the harvestman’s potential danger, but this animal poses no threat to humans or pets. Harvestmen lack venom glands entirely, meaning they are not venomous and cannot inject toxins. The myth that they are the most venomous creature but cannot bite a human is false.
They are timid and non-aggressive creatures that rarely attempt to bite. Even if a harvestman tried to bite a person, its tiny, pincer-like chelicerae are not strong enough to pierce human skin effectively. When disturbed, their primary defense mechanism is autotomy, where they intentionally shed a leg. The detached leg continues to twitch, serving as a distraction that allows the harvestman to escape unharmed.