March 1994: Terrific Tarantulas

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).

Figure 5 Urticating hairs are a defense mechanism used to keep predators away. The hairs are not poisonous, but can cause irritation if embedded in the skin.

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 21-24 degrees C (70-75 degrees F), no other heating is necessary. Do not allow the aquarium to get much warmer than 26 degrees C (80 degrees F), or cooler than 18 degrees C (65 degrees 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.

Molting

Housing

Study

Further Reading