Opiliones

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Common Names

Aka Harvest Men or Daddy Long legs.Daddy-long-legs/Daddy-longlegs/Daddy Long-legs, Granddaddy-long-legs, Harvest Spiders, Shepherd Spiders, Phalangids, Opilionids. The former scientific name for Opiliones was Phalangida and this name still often appears in the literature. The common name "daddy longlegs" also is used for the crane fly (Tipulidae) and the cellar spider (Pholcidae) (Crawford 2005).[encyclopedia]

Description

Opiliones are delicate, shy forms that are among the largest of arachnids in woodlands.[class book]

Easily separated from spiders by the broad fusion of the two body segments, so that the body appears to be composed of a singular segment. Harvestmen do not possess silk glands, and can't spin webs. Unlike spiders, harvestmen lack venom glands associated with their chelicerae (mouthparts). Uniquely among the arachnids fertilization is direct: males of most taxa possess a penis (also referred to in the literature as pene, aedagus or intromittent organ).[bug guide]

Harvestmen are known for their exceptionally long walking legs, compared to body size, although there are also short-legged species. The difference between harvestmen and spiders is that in harvestmen the two main body sections (the abdomen with ten segments and the cephalothorax—or the prosoma and opisthosoma) are broadly joined, so that they appear to be one oval structure; they also have no venom or silk glands. In more advanced species of harvestment, the first five abdominal segments are often fused into a dorsal shield called the scutum, which is normally fused with the carapace. Sometimes this shield is only present in males. The two most posterior abdominal segments can be reduced or separated in the middle on the surface to form two plates lying next to each other. The second pair of legs are longer than the others and work as antennae. This can be hard to see in short-legged species.

Typical body length does not exceed 7 millimeters (about 5/16 inch), with some species smaller than one millimeter, although the largest species Trogulus torosus (Trogulidae) can reach a length of 22 millimeters (Pinto-da-Rocha et al. 2007). However, leg span is much larger and can exceed 160 millimeters (over 6 inches).[encyclopedia]

Range and Habitat

Global, except Antarctica-range

forests, grasslands, wetlands, mountains, caves, chaparral, and anthropogenic habitats

As expected, Tropical realms concentrate most of the opilionofauna. The Neotropics and Indo-Malayan are the most diverse realms with respectively 2691 species (41%) and 1337 species (20%). That is, together they have almost 2/3 of the Opiliones. The third most diverse realm is the Palearctic with 819 species (13%), mostly because of its sheer size. Afrotropical has only 745 species (11%). Australasia with 564 species has 9% and Nearctic with 379 species has less than 6%. The total sum of species of all realms is slightly different from the total Opiliones because a few species are shared between realms.[zootaxa correspondence]

Species

>6600 species worldwide arranged into ~45 families of 4 suborders (of which Laniatores is by far the largest, with >4100 species) [Bug page]

ex.Laniatores: these are the stout, spiny harvestmen found in the Tropics, which may reach very large size. Dyspnoi: these are Temperate Old World species, dull-colored and short-legged. Some species may have bizarre ocular ornamentation. Eupnoi: these are the daddy-longlegs, familiar to Europeans and Americans. They have coriaceous tegument, delicate pedipalps, legs often very thin and long. There is a a myriad of tropical species (Gagrellinae), which may have mettalic shines, intricate honeycomb patterns of granulation, and striped/dotted multicolored hues of blue, red, green, yellow. Cyphs: these are the minute acari-like Opiliones which were undersampled until the last decades, when intensive studies made them much better known[museum classification page]

Activity

Most species are nocturnal and colored in hues of brown, although a number of diurnal species are known, some of which have vivid patterns in yellow, green, and black with varied reddish and blackish mottling and reticulation.[wikireal]

They are active predators during the daylight but tend to be crepuscular. [our book]

Reproduction

Although parthenogenetic species do occur, most harvestmen reproduce sexually. Mating involves direct copulation, rather than the deposition of a spermatophore. The males of some species offer a secretion from their chelicerae to the female before copulation. Sometimes the male guards the female after copulation, and in many species the males defend territories. The females lay eggs shortly after mating, or up to months later. Some species build nests for this purpose. A unique feature of harvestmen is that in some species the male is solely responsible for guarding the eggs resulting from multiple partners, often against egg-eating females, and subjecting the eggs to regular cleaning. The eggs can hatch anytime after the first 20 days, up to almost half a year after being laid. Harvestmen need from four to eight nymphal stages to reach maturity, with six the most common (Pinto-da-Rocha et al. 2007).[encyclopedia]

Noted

Although harvest men are a fascinating group of arachnids the dramatic increase in environmental disturbance around the world especially in tropical regions may have driven many species to extinction even before there formal description by taxonomists. Human activities including pesticide use forestry operations air and soil pollution fire and even the introduction of domestic animals have a tremendous impact on the habitats they depend on. All formerly considered endangered are most were cave dwellers who are particularly sensitive to disturbances of habitat [Harvard bookHarvestmen: The Biology of Opiliones Ricardo Pinto-Da-Rocha, Glauco Machado, and Gonzalo Giribet (eds.). 2007. Harvard University Press.]

Myth: The daddy-longlegs has the world's most powerful venom, but fortunately its jaws (fangs) are so small that it can't bite you. Fact: That is a full-fledged Urban Legend, with no basis in fact whatever. This legend is so widespread that many people believe it who should really know better, including some teachers and TV documentary producers.

Three different unrelated groups are called "daddy-longlegs." Harvestmen have no venom of any kind. None at all! Same with crane flies . Pholcid spiders have venom (like almost all spiders) but there's nothing special about it; in fact, a recent study showed that pholcid venom is unusually weak in its effect on insects. This myth is debunked at greater length on Rick Vetter's website.[Burke museum paper]

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