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.
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.
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.
- Cyphophthalmi – mite harvestmen
- Palpatores – daddy longlegs
- 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