ANSWERS TO COMMON QUESTIONS ABOUT HARVESTMEN (OPILIONES or PHALANGIDA)


Prepared by some members of the Opiliones Internet Discussion Group: Luis Acosta (Argentina), Chemeris Aleksey (Russia), James Cokendolpher (U.S.A.), Robert Cunningham (Thailand), Gonzalo Giribet (U.S.A.), Pedro Gnaspini (Brasil), Robert Holmberg (Canada), Adriano Kury (Brasil), Rogelio Macias-Ordonez (Mexico), Ricardo Pinto-da-Rocha (Brasil), Bill Shear (USA), Nobuo Tsurusaki (Japan). The Opiliones Internet Discussion Group provides a forum for the discussion of all aspects of Opiliones. Anyone interested in these animals is welcome to participate. Currently, there are no archives or digests, and the list is not moderated. You can subscribe to this list by sending the message:

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to mailserv@hsc.edu. Any unresolved problems regarding subscription to the list should be addressed to Bill Shear at bills@hsu.edu.


QUESTIONS

Are harvestmen Opiliones?
Are Opiliones the same as Phalangida?
Are Opiliones spiders?
Are daddy-long-legs Opiliones?
Can Opiliones bite people?
Are daddy-long-legs poisonous to humans?
Why does an Opiliones stink when I pick it up?
What do Opiliones eat?
Do Opiliones chew their food?
Do Opiliones produce silk or webs?
Why are some Opiliones found in big aggregations?
How many kinds of Opiliones are there?
Are any Opiliones endangered
Why do Opiliones legs twitch after they are detached?

ANSWERS

Are harvestmen Opiliones?

Yes, like daddy-long-legs, harvestmen is a common name used in the English language for Opiliones. These animals are known by a variety of other common names in different languages: arañas patonas (Spanish, parts of Mexico), carter (English), chichina (Spanish, Pampa de Achala, Argentina, for Pachyloidellus goliath), chinchina (Spanish, Sierras de Cordoba, Argentina, for Pachyloidellus butleri), falangia (Spanish), father-longlegs (English), Faucher (French), Faucheux (French), granddaddy-long-legs (English) Harry-longlegs (English), hooiwaens (Afrikaans, South Africa), Hooiwagens (Dutch), Kanker (German), Kaszáspókok (Hungarian), Kosari (Ukrainian), kosci (Croatian), koscov (Slovak), Lockespindlar (Swedish), Lukit (Finnish), mekuragumo (Japanese), Mejere (Danish), opilión (Spanish), opiliao (Portuguese), Opilions (French), Opilionidelor (Roumanian), Opilionidi (Italian), pinacates (Spanish, parts of Mexico), sacabuches (Spanish, parts of Mexico), sekáci (the c has a "v" over it) (Czech), Senokostsy (Russian), shepard-spiders (English), suhe juzine (Slovene), tanganas (Spanish, parts of Mexico), Weberknechte (German), Zimmermann (Swiss).

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Are Opiliones the same as Phalangida?

Yes, Phalangida is an old scientific name for Opiliones. Opiliones is the currently preferred usage, but you may still find these animals referred to as Phalangida in older and some recent literature. Phalangida and Opiliones are both names for a subgroup (Order) of the Class Arachnida (8-legged arthropods). Some other Orders of the Arachnida include the scorpions (Scorpiones), spiders (Araneae), and ticks and mites (Acari).

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Are harvestmen spiders?

Harvestmen are arachnids (8-legged arthropods) but NOT spiders. Spiders are also arachnids. Spiders have two body parts (fused head-thorax and abdomen), two fangs, and produce silk. Harvestmen do not produce silk (like spiders), have no fangs, and have one body part, not two as in spiders, nor three as in insects. Spiders have waist, Harvestmen do not.

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Are daddy-long-legs Opiliones?

Yes and no! In English, there are three different groups of animals commonly called daddy-long-legs. They are:
(1) Opiliones [although many kinds (species) have short legs],
(2) cellar or daddy-long-legs spiders (these are true spiders which belong to the Family Pholcidae,
(3) adult crane flies (true flies of the Order Diptera, Family Tipulidae). Tipulids look like large mosquitoes but cannot "bite." Like most insects, they have three body parts (head, thorax, abdomen) and, like most flies, they have only two wings.

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Can havestmen bite people?

Not really. Harvestmen or Opiliones can pinch the skin with their chelicerae (i.e., claws with a moveable finger like a crab claw) but seldom can penetrate human skin. However, some have sharp spines that can cause bleeding. Some also can pinch hard with their back legs and cause considerable pain. These spines are especially found in males of some larger species in South America.

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Are daddy-long-legs poisonous to humans?

Maybe and No. Depending on weather you are asking about the daddy-long-leg spider or the daddy-long-leg Opiliones (see question above about daddy-long-legs). Opiliones have no fangs or venom glands. They do have defensive secretions produced by a pair of scent glands on the front end of the body but these secretions can not be injected by their mouth parts. Some people may be sensitive to the scent gland secretions but this would affect them through their lungs or through skin contact, not through bites. In very old publications (hundreds of yeas ago), the term Phalangid was used for many different animals, some of which were poisonous to humans. As discussed above, daddy-long-legs spiders are true spiders and have venom and fangs but it is a myth that pholcid spiders have venom that is highly toxic to humans. In other words, unless you develop an allergic reaction to pholcid bites, you should have no worries.

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Why does an Opiliones stink when it is picked up?

This smell is created to help the Opiliones defend itself. On the front of the body (slightly in front and to the sides of the eyes) are two pores from which the defensive material is secreted. Next time you pick up an Opiliones, look to see if a drop of fluid is formed in this region. Smell the Opiliones and then after releasing it smell your fingers. Was the Opiliones successful in getting the smelly fluid on your fingers (see also the question about daddy-long-legs being poisonous to humans)? If you were a small predator (mouse, bird, spider, etc.) and grabbed the Opiliones, you would get a mouthful of this smelly material. Some of the chemicals produced are quit nasty and would burn the eyes and mouth of the predator with the result of the animal releasing the Opiliones.

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What do Opiliones eat?

"Everything", almost. There are many kinds of Opiliones and some seem to have distinct preferences in what they eat while most seem to be less choosy and eat almost anything, especially animal matter. Some species are predatory on small insects, snails, worms, etc., whereas others walk around nibbling on plants, fruits, and dead material that they find. In captivity, you can try feeding your Opiliones freshly chopped meal worms or other juicy insects. Oatmeal, a little piece of fruit or nut might also be eaten.

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Do Opiliones chew their food?

Yes, they chew their food. They ingest particles of food, not just juices.

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Do Opiliones produce silk or webs?

No. Some old literature suggest that Opiliones do produce silk, but this has not been proven. These reports of silk production were based upon finding small strands of what the authors thought were silk in a box which had housed Opiliones. The shed skins of Opiliones are sometimes found hanging from a thread of silk. In these cases it is assumed that this silk was made by spiders and adapted to the use (holding onto while shedding the skin) by the Opiliones.

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Why are some Opiliones found in big aggregations?

This is indeed a good question. Nobody knows for sure, but scientists are investigating this behavior. It appears different kinds of Opiliones aggregate for different reasons. Some apparently aggregate to create or maintain a desirable microhabitat (temperature, humidity, darkness, etc.). Other aggregations appear to be for purposes of hibernation or rest. It may be possible that the defensive secretions of a mass of Opiliones would be more effective than those of a single individual. Also, the aggregations tend to pulsate wildly when bothered- a huge pulsating mass could be intimidating to predators.

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How many kinds of Opiliones are there?

There are Worldwide about 7,000 described kinds or species, but there are many, many more that are not named by scientist yet.

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Are any Opiliones endangered?

Yes! Numerous species of Opiliones are endangered but only a few receive any kind of governmental protection. Opiliones, like other kinds of plants and animals, can be in danger of extinction without anyone ever noticing the threats to their existence. All Opiliones which occur in very restricted habitats can be endangered if human activities unfavorably alter the habitat. Troglobitic (animals totally restricted to life in caves) Opiliones are endangered if their home caves are in or near cities where pollution and development of the land can alter the cave habitat. Opiliones found in very restricted habitats around desert springs or mountain tops can also be endangered if the habitat is being changed. Invasion of exotic animals can also endanger Opiliones. In some areas the invasion of fireants into caves has threatened the cave environment.

All troglobitic species (of all animal taxa) are considered to be at least threatened in Brasil. Thus far, the only Opiliones on a red list for the state of São Paulo is Pachylospeleus strinatii from caves.

Scientist in Argentina know of several Opiliones which appear to be "vulnerable", if not endangered. These include Pachyloidellus fulvigranulatus, which is found only on top of Cerro Uritorco, the highest peak in the Sierras Chicas chain (provincia de Cordoba) and Pachyloides borellii is in rainforest patches in NW Argentina which are in an area being dramatically destroyed by humans. The rainforest patches are natural (in that area) and probably act as "islands" P. borellii There is some morphological variation between different isolates of the species, each seemingly being endemic to one patch. These are too small and are gradually being reduced by human action. So there is a real danger that some geographic variants (subspecies?) of P. borellii will disappear in the near future. The cave living Picunchenops spelaeus is apparently endangered through human action. So far no harvestman has been included in any kind of a Red List in Argentina and therefore they receive no protection..

Maiorerus randoi has only been found in one cave in the Canary Islands. It is included in the "Catálogo Nacional de especies amenazadas" (National catalog of threatened species) from the Spanish government.

Texella reddelli and Texella reyesi are listed as endangered species in the U.S.A. Both are from caves in central Texas. Texella cokendolpheri from a cave in central Texas and Calicina minor, Microcina edgewoodensis, Microcina homi, Microcina jungi, Microcina leei, Microcina lumi, and Microcina tiburona from around springs and other restrictive habitats of central California are being considered for listing as endangered species, but as yet receive no protection.

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Why do Opiliones legs twitch after they are detached?

The legs continue to twitch after they are detached because there are pacemakers located in the ends of the first long segment (femur) of their legs. These pacemakers send signals via the nerves to the muscles to extend the leg and then the leg relaxes between signals. While some Opiliones legs will twitch for a minute, other kinds have been recorded to twitch for up to an hour. The twitching has been hypothesized as a means to keep the attention of a predator while the Opiliones escapes.

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