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

In Part I of this article, we learned that less than 1% of the world’s 40,000+ spider species are dangerously venomous.  Today I’d like to highlight their valuable role as insect predators and point out a few reasonable precautions that should be taken when keeping spiders in captivity.

Hunting Methods and Diet

Spiders consume animals ranging from mites to birds.   Not all ensnare their prey in webs…some hunt by running (wolf spiders), swimming (European diving bell spider), spitting silk (spitting spider), hiding in flowers (crab spider), throwing webs (bolas spider), luring fishes while floating (fishing spiders) or rushing from burrows fitted with hinged doors (trap door spider).

However, all spiders consume insects, including agricultural pests and disease-bearing species, to some degree.  Field research has shown that harmful flies comprising over 60% of the diet of certain web-building species.  It is estimated that the weight of the insects consumed yearly by spiders in New Zealand exceeds that of the island’s human population!

Precautions – Bites and Urticating Hairs

The fact that so few spiders are dangerous to people should not be taken as a license to ignore caution when dealing with them. Just as with bees and other venomous animals, allergic persons can be injured or killed by the bites of relatively benign species, and potentially fatal infections can be associated with the bite of any animal.

Also, many tarantulas shed urticating (irritating) 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.

That being said, 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 plastic tongs or by ushering them into a container.

Further Reading

The diving bell spider is certainly one of the world’s most interesting invertebrates – living within a submerged shelter that exchanges oxygen with the surrounding water and swimming after small fishes!  To read more, click here.

 

Misumena vatia with wasp image referenced from wikipedia and originally posted by Olei.

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

Note: Please see Tarantulas in Captivity: An Overview of Popular Species for information on other species and an overview of tarantula-keeping.

 

Sri Lankan Ornamental Tarantula, Poecilotheria fasciata

Beautifully colored in gray and greenish-brown with an overlying pattern of light gray, these striking, arboreal tarantulas hail from Sri Lanka and neighboring southern India.  The undersides of the first 2 pairs of legs are bright yellow, adding greatly to the effect of their threat display.

Although they do well in captivity, it must be remembered that these spiders are fast-moving and high strung, with possibly the most powerful tarantula venoms known (such has not proven dangerous to people, but, as with all venoms, the potential for severe allergic reactions exists).  They should not be handled.

 

Ornamental tarantulas should be housed in a tall terrarium with ample climbing surfaces.  A hollow branch or bamboo stick should be provided as a hiding spot – unlike pink-toed and other arboreal spiders, ornamental tarantulas do not construct substantial silken retreats.  They occur in habitats subjected to a prolonged dry season – in captivity, a daily misting of water will satisfy their needs. Ornamentals are one of the few tarantulas that can sometimes be kept in groups (the pink toed tarantulas, Avicularia spp., are the other; please see Part I of this article for cautions) – several spiderlings have even been observed feeding upon the same insect!  Their diet should consist of roaches, crickets, waxworms and wild-caught insects such as moths.

 

Suntiger Tarantula, Psalmopoeus irminia

Venezuela’s suntiger is quite large for an arboreal tarantula, and strikingly marked in black and red.  These qualities, and its relative hardiness, have added to its popularity in recent years – in fact, this species has even been hybridized with the closely related Trinidad chevron tarantula,

P. cambridgei (the offspring are sterile and not brightly-marked). 

 

Suntigers require high humidity and should be kept in a tall terrarium over a moist substrate  and sprayed with water daily.  Clumps of damp sphagnum moss  wedged among the branches and other climbing surfaces will also help in maintaining moisture levels.

Ravenous predators (feed them crickets, roaches, waxworms, moths and other insects) and quick to “take offense”, these beauties live up to the “tiger” portion of their name quite well!

 

Haitian Brown Tarantula, Phormictopus cancerides

This species was formerly imported in large numbers, and was relatively inexpensive for such a large spider.  The state of Florida now prohibits its sale, and importations have fallen off, but captive-hatched animals are regularly available.

 

Native to Hispaniola (Haiti and the Dominican Republic) and Puerto Rico, with close relatives in Cuba, this large, ground-dwelling spider is dark brown in color.  The males are infused with an attractive purple iridescence.  Field reports indicate that they are less likely than other tarantulas to use a specific shelter, and may wander about in search of prey in the manner of wolf spiders.

 

Haitian browns should be kept on a moist substrate  and provided with a cave  in which to hide.  Females are long-lived, easily reaching the 20 year mark in captivity, but their size and willingness to bite and shed urticating hairs renders them unsuitable for those new to tarantula-keeping.  In common with tarantulas from similar habitats, Haitian browns relish earthworms (worms are usually rejected by arboreal and desert-dwelling spiders).  They will also take crickets, roaches, wild-caught insects and dead pink mice.

 

Mexican or Arizona Blond Tarantula, Aphonopelma chalcodes

This is one of the few North American tarantulas to have become popular in the pet trade, and with good reason – adapted to the harsh conditions of their Sonoran Desert (southern Arizona and northern Mexico) home, females can reach ages of 20 years or more in captivity.  It is also a beautifully-marked spider that exhibits an unusual degree of sexual dimorphism – females are tawny brown with dark basal (close to body) leg segments, while males are slate blue with orange to reddish abdomens.

 

Mexican blond tarantulas construct burrows of up to 2 feet in length, the entrances of which are covered with silk by day, apparently to conserve moisture.  This species’ life history is strongly influenced by environmental conditions and its activity levels are cyclical in nature.  The spiders may remain sealed within their burrows for 6 months at a time, while in July and August the males wander about en masse in search of females.

 

Mexican blonds should be housed in a terrarium with a deep (they do best if allowed to construct burrows), dry substrate of gravel and sand.  They are quite docile, but this should not be taken to mean that they can be carelessly handled (please see Part I of this article).  Like all desert-adapted spiders, they require but a light misting of water every few days, and are prone to fungal infections if kept under damp conditions.  Captive-born Mexican blond tarantulas, even those several generations removed from the wild, seem tuned to an “internal clock” and may go off-feed for extended periods.  As they store a great deal of food in the abdomen, and have experimentally gone without feeding for up to 2 years, this is not a concern for healthy individuals.

 

Oklahoma Brown Tarantula, Aphonopelma hentzi

This native of the American Midwest is only rarely encountered in the trade, and its care is similar to that of the Mexican blond tarantula (see above).

 

I mention it here due to an interesting peculiarity in its natural history.  The burrows of this spider are often inhabited by the 1 ½ inch long Great Plains narrow-mouthed toad, Gastrophryne olivacea.  Despite the amphibian-eating propensities of most tarantulas, the toad remains unmolested by its huge host.  Possibly, it is protected by skin toxins or, it is theorized, the toad performs a service by consuming tiny flies, ants and other insects that might parasitize the tarantula or consume its eggs.  The toad, in return, receives a safe, moist home and the protection of an aggressive predator.

 

Scores of other tarantulas and spiders, as well as scorpions, millipedes, pill bugs, centipedes, mantids, roaches and other invertebrates, make fascinating terrarium subjects.  It has been my good fortune to have studied a number of species in the wild, and to have helped establish the Bronx Zoo’s invertebrate collection.  I will post addition invertebrate-oriented articles from time to time. 

 

A comprehensive, well-illustrated article on tarantula biology and natural history is posted at:

http://www.thebts.co.uk/old_articles/natural.htm

Although only 906 of the world’s 40,024 spider species are tarantulas (Family Theraphosidae), these interesting creatures are the best known of the group and among the most sought-after of invertebrate pets. Reptile enthusiasts, myself included, seem particularly drawn to them, hence their inclusion in this blog. Today I would like to provide an overview of the group and specifics concerning some readily available species. Future articles will cover care and breeding in detail.

Please Note: Tarantulas, like all spiders, manufacture venom and are capable of delivering a painful bite. Human fatalities from bites are unknown, but their venoms are relatively unstudied, and an allergic reaction is always possible. New World species also possess urticating (irritating) hairs, which are shed when the spider is disturbed. A colleague of mine required surgery to remove hairs shed by a Mexican Red Knee Tarantula (a relatively docile species) from his eye. Do not handle tarantulas, despite what you may see others do – move the spiders, if at all, by urging them into a plastic container, and wear goggles where appropriate. Please also check the legalities of tarantula ownership – several species are protected by law; others are prohibited in some states.

Tarantulas in General
Tarantulas range in size from those that mature at 1 inch in length to behemoths with 12 inch leg spans, and may be ground-dwelling, fossorial (burrowing) or arboreal. Females of several species can reach 30 years of age (most males live but 1 or 2 years).

They are found in tropical, sub-tropical and (less commonly) temperate regions of Africa, the Middle East, southern Asia, Australia, New Zealand, the Indo-Pacific, Micronesia, Central and South America, the southern half of the USA and throughout the Caribbean. Various species are adapted to live in deserts, open forests, grasslands and rainforests. A number also thrive around people, and may be found in overgrown fields, agricultural areas, gardens and even within homes.

Although considered to be “primitive” spiders, tarantulas are quite successful as a group, and are the dominant invertebrate predators in many environments. They take any animal that can be overcome, including spiders, centipedes and other invertebrates as well as snakes, frogs, lizards, mice and other small rodents. The name “bird-eating spider” was first applied to the group in 1705 when Swiss naturalist Maria Sibylla Merian included, in a book on the insects of Suriname, a painting of a pink-toed tarantula consuming a hummingbird.

Tarantulas are distinguished from other spiders by their book lungs (unique respiratory organs), the presence of 2 claws and adhesive pads on the tips of the legs and by the fact that they use their fangs in an “up and down” as opposed to “side to side” motion.

Goliath Bird-eating Tarantula, Theraphosa blondi
This rich-brown spider is the undisputed king of the trade and, with a leg-span approaching 12 inches, of the spider world as well. Relatively unknown here until the early 1980’s (please look for my future note concerning my early experiences with them), captive born goliaths are now readily available. This animal is not, however, for the beginner – they are extremely aggressive and fairly demanding as captives.

Native to the rainforests of northeastern South America, goliath birdeaters require high humidity in captivity and a terrarium of at least 20 gallons in size. They should be provided with deep, moist substrate in which to burrow, or an artificial cave . Adults are fully capable of overcoming an adult mouse, but such is not recommended as food (dead mice are accepted). They fare well on roaches, earthworms, crickets and wild-caught insects such as grasshoppers and katydids.

Mexican Red Knee Tarantula, Brachypelma smithi
Quite different from the goliath in color, temperament and captive needs, the red knee is responsible for the advent of tarantula keeping in this country. Jet-black with bright red-orange leg joints, this spider is quite calm in temperament (but can bite and shed urticating hairs, see above) and hardy. One that I received as an adult lived for 18 years, putting its total age at over 23, and similar records are common.

The red knee hails from western Mexico, and is tolerant of quite dry conditions (recent hatchlings need a fairly moist environment, however). It does well on a sand-gravel substrate and readily accepts crickets, roaches, newly-molted super mealworms and wild-caught insects. This species is now protected by the Mexican government, but captive-born specimens are commonly available.

Pink-toed Tarantula, Avicularia avicularia
Unlike the previous 2 spiders, the pink-toed tarantula (named for its pink-tipped “toes”, or tarsi) is strictly arboreal. It is also unique in that it is encouraged, rather than displaced, by human activities. Various species range from the Caribbean south to Peru, and readily colonize homes, gardens and parks.

Pink-toed tarantulas construct a thick, silken retreat on tree trunks, roof eves and among plants (where they will often bind 2 leaves together to form sturdy walls for their homes). They prefer moderate humidity, but are fairly tolerant in that regard. Oddly for a spider, pink toed tarantulas get along fairly well in groups, with 2-3 individuals usually co-existing in a tank of 20 gallons or so in size. They should be kept in a vertically-oriented terrarium (an aquarium turned on end works well) furnished with cork bark, bamboo and other climbing surfaces. Pink toes relish moths and other wild-caught insects, but also fare well on crickets, roaches and waxworms.

Thailand Black Tarantula, Haplopelma minax
This Southeast Asian native is the first of the Old World species that we will cover. Like all, it lacks urticating hairs, but more than compensates for this with its extremely aggressive nature and willingness to bite. They are also quite fast, and should not be handled. Threatened individuals rear up on their back legs to expose the large fangs – which, highlighted against a red-colored patch and often tipped by a drop of venom, are intimidating in the extreme. I have observed several to fall right over onto their backs during the threat display – a position from which, it would seem, an enemy could not approach without being bitten (I have not tried, nor will I!).

This species requires a moist substrate into which it can burrow and, being high-strung, does best with minimal disturbance. A night-viewing bulb will enhance your ability to watch the spider go about its nightly activities. Thailand black tarantulas should be fed earthworms, roaches, crickets and wild caught insects such as moths and grasshoppers.

The photo accompanying this article shows a Thailand black tarantula in typical tarantula hunting position – poised at the burrow’s entrance, ready to pounce upon prey or retreat from an enemy. The silk that you see is used to provide stability to the burrow’s walls and most likely alerts the spider, via vibrations, of approaching animals. It is not, and this hold true for all tarantulas, used to ensnare prey.

 

You can access a wealth of tarantula-related resources at:
http://www.exoticfauna.com/