Terrific Tarantulas

Robert J. Wolff, Ph.D.
From the Biology Department,
Trinity Christian College, Palos Heights, Illinois 60463

The name "tarantula" means a variety of things to different people. It can mean the wolf spider from southern Italy, with its somewhat toxic bite, or the tailless whipscorpions, who belong to the family Tarantulidae. Or to many people, tarantula simply means any large, frightening spider they come across. Primarily, however, tarantula means the generally large, hairy spiders that belong to the family Theraphosidae.

Spiders belong to the order Araneae, and the majority are considered true spiders, whose fangs point to the midline and open sideways. In contrast, fangs of the order Mygalomorphae open parallel to the long axis of the body. Mygalomorphs include the trapdoor and purseweb spiders, as well as those that are commonly called tarantulas and belong to the Theraphosidae.

Structure

Tarantulas are hairy, large (35 mm or more in length), and have the basic morphology of the true spiders (Fig. 1), including two body regions, the cephalothorax (prosoma) and the abdomen (opisthosoma). The appendages of the cephalothorax include four pairs of legs, a pair of pedipalps, and a pair of fang-tipped chelicerae. The abdomen differs from that of the true spiders by having posteriorly only two pairs of spinnerets rather than three pairs, and by having ventrally two pairs of booklungs rather than one pair.

You can usually identify mature males by the special copulatory organs (palps) on the pedipalps, and by the hooks on the first pair of legs (Fig. 2). Adult females are not as easily identifiable because they often lack obvious external clues; only size and (in some) a swelling in the genital area at the ventral slit, called the epigastric furrow, allow a guess.

Behavior

Tarantulas may reach sexual maturity in as few as two years (fast-growing arboreal species in the tropics), or in as many as nine years (burrowing species). Males do not molt after reaching maturity, and soon after, adults usually begin wandering in search of females. Before copulation, a male takes up into his palps sperm that he has deposited on a specially spun sperm web. During copulation, he inserts the sperm into the female's genitalia. Males do not live more than a few months after mating. Females live longer, often reaching beyond 25 years in an appropriate environment.

Tarantulas will normally eat any prey in the right size range, including most insects, other invertebrates, and even some small vertebrates. Tarantulas may specialize on certain prey, such as millipedes or desert beetles. Based on the little research that has been done, you should feed tarantulas a variety of insects to ensure that they obtain all the needed nutrients. Normally, feeding twice a week is enough, but any live insects still not eaten within a day should be removed from the aquarium.

Handling

When handling tarantulas, always remember their safety, especially the dangers if they are dropped. If a tarantula hits its soft abdomen on a hard surface, it could break open, killing the spider. Also, you could squeeze too hard and injure the spider.

All three of the species of tarantula sold by Carolina may be handled cautiously, although only one is easy to hold. The brown tarantulas (Aphonopelma sp.) of the southwestern United States may get upset and threaten, occasionally even bite. The pink-toed tarantula (Avicularia avicularia) is an arboreal spider from South America, which is able to move quickly on any surface. While very docile and nonthreatening, its quickness may startle some students, allowing it to get away. The South American rosy-haired tarantula (Grammostola sp.) is very docile and a good spider to introduce to students.

For rosy-haired and other easily handled tarantulas, place a flat hand in front of the spider and gently touch the back legs until the tarantula eases onto your hand. The safest way to pick up a tarantula, especially one you are not familiar with, is to grab it with thumb and finger between the bases of the second and third pair of legs (Fig. 3). After gaining a little practice and familiarity, this is also the safest and easiest means of showing a tarantula to others. If a spider escapes or won't sit still, cup both hands over it; the tarantula will normally quiet down quickly in this dark, tight position.

Normally, these three species will bite only if they are being hurt. If they feel threatened, however, they may use their back legs to flick special hairs off their abdomen (see Urticating Hairs later for a full description).

While the above species may be easily handled, what about tarantulas you receive from other sources? First, if they flick their special abdominal hairs with little provocation, go slowly in handling them. Only tarantulas from North or South America have these protective hairs, and you must determine which of these may be handled. Some American tarantulas will readily bite even though they also throw the special hairs. Asian and African tarantulas do not have these special protective hairs and will often bite with little provocation or warning.

With new spiders, take a stick and touch the tarantula gently. If it rears back or displays its fangs, do not handle it. The Thailand black, for example, shows a threat display that clearly warns us to keep hands away (Fig. 4).

Urticating Hairs

The special protective hairs that are found on the dorsal and posterior surface of the abdomen of most American tarantulas are called "urticating" hairs because the hairs are barbed, and when in contact with soft tissues they dig into the tissue and cause an urtication or irritation. Five different types of urticating hairs are known. One type is laid in the webbing where the tarantula lives, preventing parasitic fly larvae from crawling into the web to attack the egg sac. Other types penetrate skin, mucus membranes, and eyes. An animal that attempts to eat the tarantula may get a faceful of the hairs, causing the eyes to water, the nose to itch, the breathing passages to swell shut, and the lips and tongue to become irritated.

Tarantulas that are very irritable or that have been mishandled frequently throw hairs. This can produce bald patches, sometimes covering almost their whole abdomen. When the spiders molt, the new exoskeleton has a complete set of new hairs.

Students should not breathe in while holding their faces at the top of the aquarium. If, while being held, a tarantula throws hairs on a student's hand, simply blow them off. Rarely can they penetrate the thickened skin of the hand, but they can embed in the soft skin of the inner arm. This spot will become red and itchy but will disappear after one or two days. If the spider throws hairs, collect them with an alcohol-dampened paintbrush and mount them on a slide to observe under the microscope (Fig. 5).

Molting

Molting is a fundamental process of all arthropods. In order to grow larger, they shed their old exoskeleton, and the new one hardens to provide protection and a place to anchor muscles internally. The new exoskeleton is larger, allowing the spider to grow internally, and it also gives the spider a complete new set of undamaged sensory and protective hairs. Molting also gets rid of any parasite or fungus that might have started to grow on the outside of the spider.

Tarantulas will normally stop feeding several days before they molt. The molting process takes several hours. It begins with the spider lying on its back, and since spiders do not die on their backs, this position only indicates molting. Do not touch the tarantula until the day after the molt to make sure the exoskeleton has hardened enough to protect it.

Housing

Aquariums provide suitable housing for tarantulas provided they have covers that prevent escape, enough space to allow air exchange yet avoid low humidity, and a substrate of gravel or vermiculite. Burrowing species (brown and rosy-haired) need a hiding place, while arboreal species (pink-toed) need to be able to climb and create a tubular silk retreat.

Water should always be available in small dishes or petri plates that are easy to clean and refill. Spraying or misting water on the arboreal materials is also beneficial as long as the materials are allowed to dry between sprays.

Temperature is important because most species are tropical or subtropical. If the room remains at a constant 21-24degrees C (70-75degrees F), no other heating is necessary. Do not allow the aquarium to get much warmer than 26degrees C (80degrees F), or cooler than 18degrees C (65degrees F). If the classroom temperature drops low at night or on weekends, a heater may be necessary. Substrate heaters are good, but avoid heat lamps or light bulbs for tarantulas.

Study

Tarantulas are not cuddly. Since they are nocturnal creatures, they spend most of the day not moving around very much. For these reasons, and sometimes because of their own fear of spiders, some teachers ignore using tarantulas. However, because of their size, docility, and ease of being held, they provide the best way to introduce students to spiders. Tarantulas are still poorly known, and therefore they make good animals to study. Keep journals of behavior, capture techniques, favorite foods, activity at different temperatures, etc. If you introduce tarantulas properly, most students quickly move from being arachnophobes to arachnophiles. With a little patience, what your class learns from tarantulas, and about spiders in general, will reward your time and care.

Further Reading

Levi, Herbert, and Lorna Levi. 1990. Spiders and Their Kin. Western Publishing Company, Inc., New York.

Milne, Lorus, and Margery Milne. 1992. The Audubon Society Field Guide to North American Insects and Spiders. Alfred A. Knopf, New York.

O'Toole, Christopher. 1993. The Encyclopedia of Spiders. Facts on File, New York.

Studying Arachnids and Insects with videos and videodiscs from Carolina

Weave and Spin

(J-C) Carolina. A study in the evolution of behavior. Traces the possible evolution of the orb web from nursery webs, sheet-webs, funnel-webs, and cobwebs. Includes details of web-spinning and prey-catching behavior. All photography by Oxford Scientific Films, Ltd. With teacher's manual. 12 minutes. 
   49-2460      Each . . $49.95

Hunters in the Grass

(J-C) Caro-lina. A survey of the hunting strategies of spiders without webs. In-cludes spiders that stalk their prey and those that lie in wait, such as purse web and trapdoor spiders. Other spiders shown catch fish, hunt under water, cast nets over their victims, and even use an implement like the South American cowboy's bola. All photography by Oxford Scientific Films, Ltd. With teacher's manual. 14 minutes. Bronze Apple, National Educational Film and Video Festival. Finalist, American Film and Video Festival. 
   49-2461     Each . . $49.95

Webs and Other Wonders

(J-C) Oxford Scientific Films, Ltd. Everyone knows that spiders spin webs; this program shows some of the other, less familiar uses they make of silk. Includes segments on the construction of an orb web and its possible evolutionary history, as well as spiders that hunt like leopards, catch fish, throw nets and bolas to catch their prey, build trapdoors, and more. 60 minutes. 
   49-2462     Each . . $74.95

Attracting Butterflies to Your Backyard

(P-C) Nature Science Network. A fascinating program that goes beyond the typical pretty collection of butterfly footage. Includes detailed information on the difference in butterflies and moths, the life cycle of butterflies, and the habitats needed for different kinds of butterflies, both as adults and as larvae. Provides excellent information on the process of planning and establishing butterfly gardens to bring these fascinating insects into living view of your students. Includes teacher's guide. 58 minutes. 
   49-2471     Each . . $29.95

The Anatomy of the Grasshopper

(J-C) Carolina. Designed for use as a supplement to or as an alternative to dissection. Covers the structure and function of the organs and systems in this representative of the phylum Arthropoda, class Insecta. All major organ systems are thoroughly covered. Includes teacher's manual. 16 minutes. 
   49-2404     Basic Set . . $49.95

Insects: The Little Things that Run the World

CAV Videodisc. Smithsonian Laserdisc Collection. Insects have been around for at least 350 million years. This program on videodisc demonstrates the stunning ways insects have evolved and adapted to survive for eons while so many other animals have become extinct, and why scientists consider insects to be the most successful living organisms on earth. See the Smithsonian's "Insect Zoo," a mecca for children and the first of its kind in the country. 
   49-8875      Each . . $39.95

Spiders in the Classroom!

Habitats and supplies for understanding mysterious arachnids Tarantula Habitat. Designed for maintaining a tarantula in the classroom. Includes rectangular plastic terrarium with lid, sand, tree branch, water bowl, and instructions. 
   L 670     Kit Only . . . . . . . . . . . . . $26.65
   L 670A    Kit with Brown Tarantula . . . . . $39.85
   L 670B    Kit with Rosy-haired Tarantula . . $58.10

Deluxe Tarantula Habitat

Designed for maintaining a tarantula in the classroom. Includes 10-gal (all-glass) aquarium, incandescent hood with bulbs, substrate, tree branch, water bowl, and instructions. Tarantulas included in kits L 670E and L 670F will be shipped approximately two weeks after kits are shipped. 
   L 670D     Kit Only . . . . . . . . . . . . . $64.25
   L 670E     Kit with Brown Tarantula . . . . . $74.80
   L 670F     Kit with Rosy-haired Tarantula . . $97.89

Tarantulas

Tarantula Set

Includes our choice of three different types of tarantulas. With care instructions. 
   L 670N     Per set . . $72.40

Tarantula

Usually a brown tarantula is shipped. Not sexed. With care instructions. 
   L 671     Each . . $14.85

Pink-toed Tarantula

A spider with a black body and pink toes. With care instructions. 
   L 674     Each . . $25.60

Rosy-haired Tarantula

A large spider with rosy-colored hair on its back. These spiders are considered to be one of the most docile tarantulas. With care instructions. 
   L 676     Each . . $43.98

Other Arachnids

Scorpion

Not sexed. Sold only to schools and businesses. With care instructions. 
   L 655     Each . . $14.50

Spiders

Not identified. A mixture is shipped when possible. With care instructions. 
   L 658A     Per 6 . . $20.65

Cellar Spiders

Family Pholcidae. Often called daddy longlegs spiders. Species and size as available. Not sexed. With care instructions. 
   L 659     Per 12 . . $20.65

Orb Weaver

Many species of this family (Araneidae) spin circular webs. Species and size as available. Not sexed. With care instructions. Residents of HI and TN must apply for USDA permit to receive this material (we will supply necessary information and forms). 
   L 662     Each . . $11.95
Plastic 11/2-gal Aquarium Made of flexible material that is break- and crack-resistant. Conveniently stacks for storage. Size, 5-1/4" D x 7" W x 11-1/4" L. Flexible, snugly fitting plastic Cover prevents escape of specimen and easily converts the aquarium to a terrarium. Dial ventilator helps control air flow. 67-0388 Aquarium (without cover) . . $6.45 $4.15 67-0389 Cover . . $5.90 $4.80

Plastic Aquarium/Terrarium

Made of a flexible plastic thaqt is break- and crack-resistant. Tank can be used as a terrarium or an aquarium and comes with a ventilated top. 
   67-0390     1/2 gal . . $3.65
   67-0391     1 gal . . $5.15 $4.50

Dry Tank Heater

A self-stick unit (1/16" thick) adheres to the outside bottom of tank. 
   67-4318     Each . . $11.25

Sizzle Stone(tm)Sizzle Stone(tm)

A vivarium heater that produces an internal heat that cold-blooded animals thrive on. With 6-ft cord. UL listed. Two sizes. 
   67-4319     For 5-20-gal Tank . . $13.95
   67-4319A     For 20 gal and Up . . $21.95

Food

Millipedes

A very large, docile terrestrial animal, also known as the thousand-legger. Has many segments, each bearing two pairs of appendages. With care instructions. 
   L 645     Per 3 . . $11.40;  12 . . $42.10

House Cricket

Acheta domesticus. With instructions. 
L 715      Adults, per 12  . . $4.95
                   per 50  . . $12.40
                   per 100 . . $19.98
L 715B     Nymphs, per 12  . . $ 5.05
                   per 50  . . $11.50
L 715C     Life Cycle Set (all stages) . . $8.79

House Cricket Food

250 g 
   L 715M     Per bag . . $4.45

Mealworms

Tenebrio. Larvae are ideal food for amphibians and reptiles, as well as spiders. With instructions. 
   L 891     Larvae, per 50  . . . $5.25
                     per 100 . . . $7.75
                     per 500 . . . $19.90
                     per 1,000 . . $29.90