Family: Phalangiidae, Sclerosomatidae
In Colorado, commonly encountered harvestmen include certain Leiobunum spp. and the invasive Philangium opilio. The most distinguishable feature of harvestmen are their very long and thin legs, with the front pair of legs held out in front of the body and are used for sensing the environment. Harvestmen most likely to be encountered in and around homes are light gray or brown. The bodies of P. opilio range from 3.5-9 mm (1/10-1/3 inch) in length. Harvestmen do not have a distinctly separated cephalothorax (fused head and thorax) and abdomen and have one pair of eyes that extend above the cephalothorax. They do not have fangs, and their chelicerae (jaws) are modified for tearing food into small pieces.
Immature forms of harvestmen resemble the adult form but are generally smaller in size. Differences in males and females of harvestmen usually appear in the nymphal stage just before reaching the adult form. These differences include males having a smaller body than females and longer legs relative to their body size.
- Harvestmen are not spiders and do not bite. They do not have fangs or venom glands and do not create webs.
- The bodies of harvestmen lack distinct body segments and have oval bodies. They have very long and narrow legs. The three hind pairs are used for movement, while the front pair of legs are used as sensory structures typically held in front of the body.
- Harvestmen are often mistaken for cellar spiders (Family: Pholcidae), which are true spiders that produce webbing and have a distinctive separation between their thorax and abdomen.
Adult Philangium opilio. This invasive species is widely distributed in Colorado and is commonly found in yards and gardens. Note the characteristic long narrow legs and globular body. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Adult harvestman (Leiobunum sp). Note the lack of fangs and mouthparts used for tearing prey into small pieces. Image credit: Joseph Berger, Bugwood.org
Ovipositor protruding from the body of a female harvestmen. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Spiders in the family Pholicidae are commonly mistaken for harvestmen due to their long legs. Unlike harvestmen, these spiders produce web and have a distinct separation between the cephalothorax and abdomen. Image credit: Joseph Berger, Bugwood.org
Life history and habits
The nymphs of most species go through six molts before reaching adulthood. They usually hang upside down while they molt, pulling legs free with their jaws. Harvestmen usually molt to their adult form in the fall during harvests, hence the common name. They can lose legs or leg segments as a defense mechanism to escape from predators. Their legs do not grow back and after detaching from the body, the leg will continue twitching to distract the predator and allow an escape. Mobility is not significantly reduced after losing one or two appendages. They can also secrete chemicals that make them distasteful to predators.
Harvestmen usually feed on insects that have soft bodies but can also scavenge dead insects and larger animals. Harvestmen can open their mouths wider than other arachnids which makes them capable of consuming solid pieces of food.
Unlike other arachnids, male harvestmen have an aedeagus (penis) that allows for direct insemination, while other arachnids typically produce a spermatophore (sperm package) that must be externally acquired by the female. Female harvestmen have a long, extend ovipositor used to lay eggs, usually in moss, moist soil, or rotten wood. Harvestmen are nocturnal and can be found in dark and damp spaces in the home such as crawlspaces, garages, basements, and sheds. Outdoors, they prefer to live under leaves, logs, and rocks. Adults often aggregate in groups in colder weather.
Chemical control is usually unnecessary as they can be removed or prevented from entering the home using the tactics described above. When chemical control is desired, P. opilio is susceptible to some broad-spectrum insecticides. However, broad spectrum insecticides can harm beneficial insects and should be avoided when possible.
Colorado State University. (n.d.). Daddylonglegs. Colorado Insect of Interest. Available http://www.wci.colostate.edu/Assets/pdf/CIIFactSheets/Daddylonglegs.pdf
Schmaedick, M. (n.d.). Harvestmen, Daddy longlegs, Harvest spider. Cornell University – College of Agriculture and Life Sciences. Available https://biocontrol.entomology.cornell.edu/predators/Phalangium.php