Daddy Longlegs: Order Opiliones

Opilionids go by many names: daddy longlegs, harvestmen, shepherd spiders, and harvest spiders. These eight-legged arachnids are commonly misidentified as spiders, but they actually belong to their own, separate group – the order Opiliones.

Description

Though daddy longlegs look similar to true spiders, there are some noticeable differences between the two groups. Daddy longlegs bodies are round or oval in shape, and appear to consist of just one segment or section. In truth, they have two fused body parts. Spiders, in contrast, have a distinctive "waist" separating their cephalothorax and abdomen.

Daddy longlegs usually have one pair of eyes, and these are often raised from the body's surface. Opilionids cannot produce silk, and therefore do not construct webs. Daddy longlegs are rumored to be the most venomous invertebrates roaming our yards, but they actually lack venom glands.

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Daddy Longlegs: Arachnids, but Not Spiders

By Debbie Hadley

Almost all Opilionid males have a penis, which they use to deliver sperm directly to a female mate. The few exceptions include species that reproduce parthenogenetically (when females produce offspring without mating).

Daddy longlegs defend themselves in two ways. First, they have scent glands just above the coxae (or hip joints) of their first or second pairs of legs. When disturbed, they release a foul-smelling liquid to tell predators they aren't very tasty. Opilionids also practice the defensive art of autotomy or appendage shedding. They quickly detach a leg in the clutch of a predator and escape on their remaining limbs.

Most daddy longlegs prey on small invertebrates, from aphids to spiders. Some also scavenge on dead insects, food waste, or vegetable matter.

Habitat and Distribution

Members of the order Opiliones inhabit every continent except Antarctica. Daddy longlegs live in a variety of habitats, including forests, meadows, caves, and wetlands. Worldwide, there are over 6,400 species of Opilionids.

Suborders

Beyond their order, Opiliones, harvestmen are further subdivided into four suborders.

• Cyphophthalmi - The cyphs resemble mites, and their tiny size meant they were largely unknown until recent years. The suborder Cyphophthalmi is the smallest group, with just 208 known living species.
• Dyspnoi - The dyspnoi tend to be dull in color, with shorter legs than other harvestmen. Some make up for their drab appearance with ornate decorations around their eyes. The suborder Dyspnoi includes 387 known species to date.
• Eupnoi - This large suborder, with 1,810 member species, includes the familiar, long-limbed creatures referred to as daddy longlegs. As one would expect in such a large group, these harvestmen vary greatly in color, size, and markings. A harvestmen observed in North America is almost certain to be a member of this suborder.
• Laniatores - By far the largest suborder, the laniatores number 4,221 species worldwide. These robust, spiny harvestmen inhabit the tropics. As with many tropical arthropods, some laniatores are large enough to startle an unsuspecting observer.

Sources

• _{Borror and Delong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson}
• _{Insects: Their Natural History and Diversity, by Stephen A. Marshall}
• _{Classification of Opiliones, by A. B. Kury, Museu Nacional/UFRJ website. Accessed online January 9, 2016.}
• _{"Order Opiliones - Harvestmen," Bugguide.net. Accessed online January 9, 2016.}