That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

While most people acknowledge that spiders perform a valuable service by consuming harmful insects, there remains the lingering belief that the vast majorities are dangerously venomous, and do more harm than good. Today I’d like to pass along some facts and figures that you may find interesting.

Venom

All spiders produce venom, but in most cases it is only potent enough to overcome the invertebrates upon which they feed. Less than 1% of the world’s 40,000+ spider species are capable of delivering a dangerously venomous bite to humans.

The Real Killers

Dogs, horses, pigs and other domestic animals, although enjoying a far more favorable reputation than spiders, actually kill and maim many more people than do our 8-legged neighbors. In fact, far more people are killed yearly in the USA by falling vending machines (I’m guessing in bars?) than by spiders or snakes!

Potentially Deadly Spiders

The most highly venomous Arachnid, Australia’s funnel-web spider (Atrax robustus), has not caused a fatality since the introduction of antivenin in 1981. In the USA, widows (Latrodectus spp.) and the brown recluse spider (Loxosceles reclusa) are potentially dangerous, but antivenin is available. The bite of the world’s largest spider, South America’s 12-inch goliath bird-eater (Theraphosa blondi), is very painful but otherwise harmless.

Other Spider-Associated Risks

The foregoing should not be taken as a license to ignore caution when dealing with spiders. Just as with bees and other venomous animals, allergic persons can be killed by the bites of relatively benign species, and dangerous infections can be associated with the bite of any animal. Many tarantulas shed urticating hairs when disturbed or even when just moving about. A colleague of mine underwent major surgery to remove such hairs, deposited on his hand by a “tame” red-kneed tarantula, from his eye.

I have kept native and exotic spiders since childhood, and have never been bitten because I do not pick up spiders with my hands. I urge you to handle spiders, if at all, with a plastic tongs or by ushering them into a container.

Further Reading

An excellent resource for those interested in spiders, the American Museum of Natural History’s World Spider Catalog is published at http://research.amnh.org/entomology/spiders/catalog/.

Please see my article Tarantulas in Captivity for information on keeping these fascinating creatures at home.

Funnel Web spider image referenced from Wikipedia and originally posted by Zinnmann

Goliath Bird Eating Spider image referenced from Wikipedia and originally posted by Dcoetzee

Having long worked with a variety of the world’s most unusual invertebrates, I had imagined myself ready for any and all surprises that might be offered by these fascinating creatures.  Yet the first tailless whipscorpion that I encountered in the wild – a huge specimen that met my gaze inside a hollow tree in Venezuela (where I was searching for yet another bizarre beast, the giant vampire bat) – stopped me in my tracks.

Although relatively harmless, these most unusual Arachnids certainly are formidable – some might say “nightmarish” – in appearance.  If you are looking to add an animal that borders on the unbelievable to your collection, look no further than these fascinating spider relatives.

Description

Tailless whipscorpions are members of the Arachnid order Amblypygi, related to but distinct from the spiders and scorpions.  The incredibly long front legs have evolved into sensory organs, and are slowly moved back and forth, touching this and that, as the animal senses its way about.  It really is quite a sight to behold – one simply has no frame of reference, no matter how many odd creatures have crossed one’s path.

These specialized legs may cover a span of over 1 ½ feet. Some of the larger tropical species also sport 8 inch long “regular legs” and flattened bodies exceeding 2 inches in length – very impressive beasts over-all.  Huge pinchers, kept close to the body until needed to grasp meals, add to the effect.

Tailless Whipscorpions in Captivity

The huge Tanzanian giant tailless whipscorpions (Damon variegatus and D. diadema), are becoming increasingly popular with invertebrate enthusiasts, with captive reproduction now regularly recorded.  I have housed similarly-sized individuals in groups without incident, and was even successful in breeding them in this situation (I removed the youngsters to prevent predation).

In common with all related species, Tanzanian giants are arboreal, and need wide, flat climbing surfaces.  Cork bark slabs are ideal.  They should be provided a varied diet consisting of crickets, waxworms, roaches, locusts and wild caught insects.

All species kept to date require very damp conditions and temperatures of 72-76 F.  Despite their tropical origins, tailless whipscorpions are most often found in caves, wells, hollow trees and other cool micro-habitats.  Most fail to thrive if kept warmer than 80 F.

Although lacking venom glands, tailless whipscorpions can break the skin with their formidable front claws.  For this reason, and because they move very quickly and shed legs easily, these odd creatures should not be handled.

Further Reading

You can learn more about the natural history of African tailless whipscorpions at http://www.arc.agric.za/home.asp?pid=4078.

Image referenced from Wikipedia and originally posted by Luis Fernandez Garcia

Note:  Please see Scorpions in Captivity – An Overview of Popular Species, Part I for general natural history and captive husbandry information.

Asian Forest Scorpions, Heterometrus spp.

Several species that superficially resemble emperor scorpions are sometimes available in the trade.  Known collectively as Asian forest scorpions and hailing from Southeast Asia, the most commonly seen is Heterometrus spinifer.  Like the emperor, it is jet black in color, but the claws have fewer spikes and its maximum size is 6 inches.

Basic Care

I keep Heterometrus in much the same way as I have described for emperor scorpions (Please see Scorpions in Captivity – An Overview of Popular Species: The Emperor Scorpion, Pandinus imperator).  Like their African cousins, Asian forest scorpions are also quite social…a group of 10 that I housed together in an exhibit at the Bronx Zoo co-existed for years without incident.  They seem to be quite temperature sensitive, and are best maintained at 78-85 F.  The gestation period is 5-8 months and sexual maturity is reached in 1-3 years.

Asian forest scorpions are somewhat more high-strung than emperors, and sting readily.  Heterometrus spinifer is not considered dangerous to healthy adults, but the closely related H. swammerdami of India (which, at 10-12 inches in length, is among the world’s longest scorpions) has reportedly caused fatalities.

Asian forest scorpions and emperor scorpions are both classified within the Family Scorpionidae.  Further information and a complete listing of all related species is available at http://www.ub.ntnu.no/scorpion-files/scorpionidae.php.

The basic care of this scorpion parallels that which I described for emperor scorpions in the article Scorpions in Captivity – An Overview of Popular Species; Part II: The Emperor Scorpion (Pandinus imperator). I’ll highlight species-specific information below.

South African Rock Scorpion, Hadogenes troglodytes

Ranging throughout much of southern Africa, this scorpion giant (7.5 to 8.5 inches in length) is always found in association with rocky places, especially the savannah-based outcroppings know as kopjes.  A thoroughly flattened body suits it especially well for climbing among and hiding within rock piles, a habitat it shares with the similarly-shaped flat rock lizards (Platysuarus spp.) and pancake tortoise (Malacochersus tornieri).

Color Variations

Rock scorpions vary greatly in color from population to population, and usually closely match the rocks of their habitat in hue.  Tan, reddish, brown, olive and yellow specimens, and a variety of shades in-between, all appear in the pet trade from time to time.

Captive Habitat

In captivity, they should be supplied with ample climbing opportunities in the form of rock piles and plastic reptile shelters   and caves.  If you use natural rocks, be sure to place the base of the pile directly upon the terrarium floor, not on sand, so that the scorpions do not burrow below and become crushed.  Repti sand makes a fine substrate.

The rock scorpion terrarium should be kept dry, with a light spraying of water once every 3-4 days being enough to supply their moisture requirements.  A water bowl is not necessary.

Rock scorpions are rather shy and high strung, much more so than their more commonly-kept relative, the emperor scorpion.  They will not thrive if forced to remain exposed.  Given secure shelters, however, they readily settle into captive life and may very well reproduce once habituated.  They are fairly slow-moving and seem to rely mainly upon their claws for defense.  Their venom is not considered to be dangerous to healthy adults.

An American Museum of Natural History field report detailing Hadogenes natural history and the description of 2 new species is posted at:

http://research.amnh.org/users/lorenzo/PDF/Prendini.2006.AMN.Hadogenes.pdf

Please see Part I and II of this article for information on scorpion natural history and further details on emperor scorpion care.

The captive reproduction of emperor scorpions is a most interesting endeavor (for hobbyists and, I imagine, the scorpions themselves!).  When properly housed and cared for, emperor scorpions are relatively easy to breed.  This is surprising, given that they are such unique and highly specialized creatures, and is an opportunity that should not be missed.  Many prominent invertebrate specialists started out with this species…keeping them is a wonderful way of becoming involved in invertebrate husbandry, and will almost certainly “hook” you for good.

Distinguishing the Sexes

In captivity, as within certain parts of the natural range, mating may occur during any month.  Adult females are longer and stouter than males, but this is not a reliable means of distinguishing the sexes.

There are some slight differences in the shape of the genital openings.  View the scorpions from below, in a clear plastic box, when attempting to sex in this manner – do not restrain them via hand or tongs.  Photos of the undersides of male and female emperor scorpions are posted at http://www.pandinusimperator.nl/EN/biology_EN.htm.

Courtship and Mating

Reproduction is most likely to occur if your scorpions are housed in a large terrarium that provides ample burrowing opportunities.  All species studied thus far perform a “mating dance”, with the pair locking claws and moving about.  It is theorized that this helps to clear a patch of ground for the deposition of the males’ sperm packet.  I imagine, but have not been able to determine for sure, that the specific dance “moves” also aid in species’ recognition among these nearly blind creatures (this is the case in “dancing” scorpion relatives, such as jumping spiders).

The male deposits a sperm packet on the ground and pulls the female over it (it is tempting here to draw analogies to salamander reproduction).  Hooks along the edges of the sperm packet latch onto the female’s genital opening, and the eggs are then fertilized internally.

Gestation and Birth

Gestation is highly variable, ranging from 7-10 months on average but sometimes exceeding 1 year.  It is likely that stress, temperature and other factors play a role in determining the length of the gestation period.

Females continue to feed while gravid, and may swell noticeably…when viewed from above, the carapace segments appear widely spaced, and seem ready to split apart (heavily-fed scorpions of either sex, however, may also appear gravid).

The young (sometimes called “scorplings”), 8-30 in number, are born alive and measure about 5/8 of an inch in length.  They are white in color and remain on the female’s back until their first moult, at which time they darken and begin to venture off on their own.  Once this occurs, they will readily accept ½ inch crickets, small waxworms, newly molted mealworms, wild-caught insects and canned silkworms.

Maternal Care of the Young

Female emperor scorpions feed their young with finely-shredded insects – this really is something to see.  By all means, try to do so by viewing yours at night with the aid of an incandescent “nocturnal” bulb.  The degree of care they provide to their young is extraordinary, and is far greater than one might expect from such supposedly “primitive” creatures.  Even among those scorpions that exhibit social behavior, emperors stand out as being very advanced in this regard.

Caring for the Mother and Her Brood

Once the female has given birth, all other scorpions should be removed from the terrarium, as she will become highly aggressive and defensive.  Do not relocate the mother…this inevitably stresses her and may cause her to consume her young.

Females with young react aggressively to any disturbance, even occasionally grabbing and eating scorplings that become dislodged from their backs.  This is not an uncommon occurrence – do not remove the remaining young unless she begins eating them regularly, as the overall survival rate is improved when clutches are reared with their mother.  I have raised several clutches to adulthood with the mother present – the key lies in disturbing her as little as possible and in providing a deep, secure burrow.

I usually raise the terrarium’s temperature to 85-90 F when rearing young emperor scorpions – this may not be essential, but I have found it to work well.

Sexual maturity in the wild is reportedly reached in 4-7 years, but captives may breed when only 12-14 months of age.  Emperor scorpions under my care have reproduced at age 3 and 4 years.

The Woodland Park Zoo provides interesting information on emperor and other scorpions in nature and captivity at:

http://www.zoo.org/factsheets/scorpion/scorpion.html