Opiliones
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. Opiliones were once classified as Phalangida, which they still may be referred by in older literature. The more common name "daddy longlegs" is also used for the unrelated crane fly (Tipulidae) and the cellar spider (Pholcidae) (Crawford 2005).[encyclopedia]
Description
Opiliones are delicate, shy forms and are among the largest of arachnids in woodlands.[class book]
Opiliones can be differentiated from spiders by attention to what appears to be one body segment but is actually two fused segments. Daddy Long-legs do not possess silk glands, and can't spin webs. Unlike spiders, harvestmen lack venom glands associated with their chelicerae (mouthparts). True of all arachnids fertilization is by direct contact with female. Males of most taxa possess a penis, which is also referred as a pene, aedagus or intromittent organ.[bug guide]
Daddy long-legs are known for their exceptionally long walking legs compared to body size. Some species do have shorter legs. 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.They have a second pair of legs that 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, with some species smaller than one millimeter. The 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
Opiliones are found globally with the exception of Antarctica.
Forests, grasslands, wetlands, mountains, caves, chaparral, and even human dwellings make for suitable Opilione habitats.
Tropical systems hold the most Opilione species. The Neotropics and Indo-Malayan are the most diverse realms with respectively 2691 species (41%) and 1337 species (20%). These two tropical regions are then home to almost 2/3 of the Opiliones. The third most diverse realm is the Palearctic with 819 species (13%), mostly because of its sheer size. The African tropics have 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 regions.[zootaxa correspondence]
Species
The estimated 6600 species worldwide are 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 sizes. Dyspnoi: these are temperate old world species, dull-colored and short-legged. Some species may have odd ocular ornamentation. Eupnoi: these are the "daddy-longlegs," familiar to Europeans and Americans. Their legs are often very thin and long. Several of the tropical species ex.Gagrellinae, may have metallic shines, intricate honeycomb patterns of vascular tissues, and striped/dotted multicolored hues of blue, red, green, yellow. Cyphs: These are the minute acari-like Opiliones which we have less information on due to being under studied until recently.[museum classification page]
Activity
Most species are nocturnal, although a number of diurnal species are known. [wikireal]
Other species of the active predators are active during the daylight but most are known to be crepuscular. [our book]
Reproduction
Although parthenogenetic species do occur, most harvestmen reproduce sexually. Mating involves direct copulation. The males of some species offer a secretion from their chelicerae to the female before copulation. Sometimes the male guards the female after sex. 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. Females often attempt to eat the eggs. 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 the formerly considered endangered 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.]
Contrary to popular belief daddy-longlegs species do not contain the world's most powerful venom, but fortunately its jaws (fangs) are so small that it can't bite you.
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]