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Spiders

Biology

These large tropical spiders belong to a group called the Mygalomorphs. They are referred to by different common names, Bird Eaters, because some people thought such large spiders would make huge aerial webs that caught suitably large prey. Tarantulas, because it was thought a bite caused the victim to reel in a delirious trance, like the dance called a tarantella. Neither is really true. They pounce on or ambush prey that is usually other invertebrates. Only occasionally do they eat small vertebrate prey. The bite of these large spiders, however, is surprisingly mild. Very few inject venom that is dangerous to people, the worst that usually happens, is the wound is about as painful as a bee or wasp sting. The good news is that the pain rarely lasts as long! Many spiders available as pets, are sold as spider-lings. These juveniles are often only a few weeks old and not much bigger than 5 mm. They are miniature versions of the adult and will eat proportionately sized prey, usually micro crickets or fruit flies. As the spider grows it will moult its outer skin periodically. The first signs are often a refusal of food and increased aggressiveness. Just before molting it will spin a silk mat and lay on it up side down, appearing dead! On no account should it be touched or interfered with. It will cast off the old skin and the emerged spider will often have re-grown any legs that have been shed and replaced any missing hair. At the time of shedding, various colour changes occur, the skin darkens and the overall colour may be slightly different. The spider may take a day or two to harden off, during which time it will not feed. After a shed, the colours will be at their best. The large spiders are among the few invertebrates that continue to moult as adults. In fact they can grow larger or smaller, depending on the available food supply.

Housing

The permanent cage need not be large, about 30 cm x 20 cm 10 cm being the average dimensions for an animal with a body length of 10 cm. The cage should be set up in a manner similar to the diagram overleaf. A heater should be installed to provide a background temperature of between 20ºC and 30ºC. This is best done with an HabiStat mat or strip taped to the inside of the back wall of a wooden cage or either side if the wall is glass or plastic. Make sure the mat acts like a radiator, so very little of it should be below the line of the substrate. It may be necessary to provide a local hot spot near 38ºC, while the coolest part of the cage should be nearer 25ºC. This heat source should be comparatively low powered to protect the animals from being burnt. The hot spot should only operate during the day for about fourteen hours in summer dropping to twelve in winter. A Dinosaur Fossil Series Hot Rock or a HabiStat controlled Basking Spot Lamp would provide heat for smaller and larger cages respectively. Small specimens are best kept in small cages or jars. To heat these small enclosures, keep them in a warm atmosphere or stand several on a heating mat or strip. Obviously the correct temperature range must be kept, so some experimenting must be done. Much of the success achieved in keeping spiders will come from the skilful manipulation of ventilation. Some of these animals require highish humidity others like it a little dryer but none can stand stagnant conditions. Fresh air moving into the cage is essential. Use the upward draughts caused by heated air rising to flush out the cage and drag fresh air in. A light misting with a hand sprayer will provide the humidity required. Some species will require the substrate to be damp but not wringing wet. Look in the literature for details of the particular species being kept.

Husbandry

Almost all species are best kept singly as they tend to be cannibalistic. Many will want to hide for most of the day so shelters should feature in the cage design.

Before any attempt to handle the spider is made, please make sure the spider cannot drop and injure itself as they are easily damaged by any sort of fall. These animals do not really like being handled, so if it is necessary to move them, coax them into a box that can be closed afterwards and then carry the spider enclosed. Many large spiders have a defence against interference in that they release irritating hairs. These extremely itchy hairs are brushed off the abdomen by the hind legs. If they get into the eyes or up the nose they could make you feel quite uncomfortable. You will not have to clean the cage out very often, every three or four months will do. This is only if you are careful and avoid problems. One of the main mistakes beginners make with their spiders is to overfeed them. If the spider only partly eats a meal, the remainder is left to rot. Lots of these putrefying corpses left around the cage will cause problems. Not only will the cage smell unpleasant, the natural recycling organisms will flourish. These include mites, which although do not directly attack the spider, may be present in sufficient numbers to be a pest.

Food & Feeding

The diet is wholly carnivorous and comprises in the main of live invertebrates. In captivity crickets and locusts form the staple diet. Mealworms can also be fed. Both crickets and mealworms can be fed Cricket Diet Plus and Mealworm Diet Plus respectively to load the insect with vitamins and minerals. Other insects that may be fed include Fruit Fly and Wax worms but these are best only given to small specimens. Potential meals are pounced upon and subdued with the fangs. Many people think large spiders kill their prey with a hefty dose of venom. Certainly they pump in a measure of venom but the process of subduing the prey has more to do with the mangling it gets from the fangs. These sharp hollow injectors are also hinged at the base. The segments they are attached to are invariably quite large and contain sizeable muscles. These are capable of drawing the fang back in a pincer movement with considerable power. The prey is pummeled back and forth through the two fangs in much the same way as a baker kneads dough. Long before the venom has had time to work the mechanical damage has extinguished any capability of resistance. This merciless pasting the spider dishes out is not some sadistic ritual that is designed to gratify human voyeurs. It is a very efficient way of getting the digestive enzymes contained in the venom into the tissue of the forthcoming meal. For despite having two awesome fangs, spiders cannot bite off pieces of food to swallow, instead they have to suck up a liquid meal like little vampires! A combination of mechanical disruption and enzymatic action renders soft parts of the prey into a nutritious liquid that is pumped into the gut but not through the fangs. Instead a tube like extension to the mouth, the hypo-pharynx is used.

Feed the insects one at a time, waiting for the spider to finish one item before offering another. You may find your spider eats two or three insects at one meal or it may refuse altogether. Spiders do not eat every day and sometimes will want to fast for a week or more. This is quite normal and should not worry you too much. One point to note is that just before and just after the spider sheds its skin it will not want to feed and offering insects and other forms of disturbance will be very annoying to the animal. A water dish kept full of fresh water should always be available. To stop small specimens drowning, a cotton wool pad is often placed in the water. It must, however, be kept wet to allow the spider a safe drink.

Reproduction

To sex a spider an adult specimen is usually required. The males are slimmer more leggy animals and some have characteristic 'hooks' on the first pair of legs.

Eggs are produced and are usually protected by the female. To grow to adult in captivity may take as short a time as a year or two but in the wild, eight or more years may elapse.

Species of Spider

Of the big spiders the Chile Rose undoubtedly makes the best pet. They are among the hardiest and least aggressive of all the species available. They are relatively inexpensive and still have interesting habits and things to learn about. Another popular species is the Mexican Red Knee. These are, however, often only available as small spider-lings.

Several other species are available from time to time. Keep a lookout at your local pet store or you could join a Tarantula Society. To find about the range of the species and their requirements, read up in one of the many excellent books that have been published or look on the Internet.