They come often exchangeed for spiders because their appearance spider-like but they belong to arachnids (8 legged arthropods). Unique among the arachnids, they possess a penis for direct copulation.

Opiliones distinguish themselves from spiders for:

• The body in a sole element, oval in shape, instead two portions (cephalothorax and abdomen, or opisthosoma and prosoma) like spiders,. The length’s body does not exceed 7 mm (5/16 inch).

• Two alone eyes in the frontal part of the body,

• No venomous glands,

• No structures capable to produce silk, so they can’t form webs.

• To be onnivori (they eat almost everything, live invertebrate prey, dead animals, juice from plants, fruits, veggies)

They are known for their very long, slender legs, compared to body size ( but some species have relatively short legs).

The second pair of legs are longer than the other and when disturbed they stand on six legs and wave the second in the air working as antennae (because their eyes cannot form images), sensing their surroundings and exploring the environment.

When threatened opiolines can loose one or more legs as a means of protection from predators (in order to keep the attention of the attackers on the loosen leg while he escapes).  In fact the leg may continue to twitch after it is detatched because there are “peacemakers” in the legs (femur) that send signals to the muscles to extend the leg:  the leg relaxes between signals. Legs continue to twitch for up an hour. A harvestmen needs only three legs to move about.

Harvestmen  have another defensive strategy: they emit a smelling fluid of foul odor from two pores situated slightly in front and to the side of the eyes.

Harvestmen are most commonly seen in late summer and fall.

They are mostly nocturnal and usually hide during the day.

Many species live aggregated apparently

• to create or maintain a desirable microhabitat (temperature, humidity, darkness, etc.),

• for purposes of defence (secretions of a mass of harvestmen would be more effective than those of a single individual and a mass could be intimidating to predators).

Harvestmen are not dangerous for humans.