Tarantula

Tarantulas are of the Phylum Arthropoda and the class of Arachnida. Of all known living organisms, the phylum Arthropoda is by far the largest group with over millions of species; it comprises of over 80% of all the world's known organisms. They live virtually everywhere; in saltwater marine environments, freshwater, terrestrial and aerial environments. Even though there are a multitude of varieties they all have same body plan. They all have body segmentation, a hard exoskeleton, and jointed appendages.

Anatomy
The Tarantula anatomy consist of four pairs of walking legs, with the body divided into two major segments (cephalothorax and abdomen), they have no antennas or mandibles, and respiration is by book lungs. They usually have four pairs of simple eyes.

Interestingly, the Zebra Tarantula was found to secrete spider silk from its feet to help it maintain a grip when climbing. Researchers tilted a tarantula on glass until it slipped a bit and caught itself. They found tiny threads between the feet and the glass. 

Reproduction
As with other spiders, the mechanics of intercourse are quite different from those of mammals. Once a male spider reaches maturity and becomes motivated to mate, it will weave a web mat on a flat surface. The spider will then rub its abdomen on the surface of this mat and in so doing release a quantity of semen. It may then insert its pedipalps (short leg-like appendages between the chelicerae and front legs) into the pool of semen. The pedipalps absorb the semen and keep it viable until a mate can be found. When a male spider detects the presence of a female, the two exchange signals to establish that they are of the same species. These signals may also lull the female into a receptive state; if so, the male approaches the female and inserts his pedipalps into an opening in the lower surface of her abdomen. After the semen has been transferred to the receptive female's body, the male will generally quickly leave the scene before the female recovers her appetite.

Females deposit 50 to 2000 eggs, depending on the species, in a silken egg sac and guard it for 6 to 7 weeks. The young spiderlings remain in the nest for some time after hatching and then disperse by crawling in all directions.

Ecology
Taratulas are nocturnal predators, killing their prey by injecting venom through their fangs. The hungry tarantula typically waits partially hidden at the entrance of its retreat to ambush passing prey. It has sensitive hairs that enable it to detect the size and location of potential victims from the vibrations caused by their movements. Some species also use their silk fibers to detect motion (when prey triggers a line). Like many other spiders, they cannot see much more than light, darkness, and movement, and use their sense of touch to perceive the surrounding world. They generally seem to choose prey on the basis of how dangerous they are perceived to be, the general size of the potential prey animal, etc. Some tarantulas succeed in occasionally capturing small birds, small mammals such as mice, and even small fish, but their ordinary prey consists of insects such as crickets (for ground dwellers) and moths (for arboreal species).

Tarantulas live in a variety of nests. Burrowing tarantulas live underground, in burrows. These burrows are either dug by the spider itself, or else are reused burrows abandoned by rodents or other small creatures. They may even find ready-made crevices. The tunnels are lined with silk and a webbed rim is formed at the entrance so as to conceal it. Other tarantulas make their homes under rocks or tree trunks or under the loose bark of trees. Still others build silken nests on trees, cliff faces, the walls of buildings or in plants such as bananas and pineapples. Tarantulas are well suited for climbing.

The Chihuahuan Desert tarantula (Dugesiella echina or Aphonopelma echina) has an enemy known as the tarantula hawk. This is a large orange and velvet blue wasp (Pepsis formosa) which paralyzes the tarantula with its stinger and buries it after laying an egg on it. The paralyzed tarantula serves as food for the young larvae. This is an example of the predator prey relationship that maintains balance in nature and is compatible with creation concepts of designed limits.

Predators of Tarantulas
Tarantulas fall prey to a variety of generalist predators including birds, lizards, snakes, frogs, toads, skunks, coatimundis, and javelina. Both small headed flies and tarantula hawks parasitize these large spiders. Small headed flies lay their eggs on the spiders; when the eggs hatch, the larvae enter the body of the spider and consume internal organs. Tarantula hawk females first sting the spider, paralyzing it, then lay an egg on it before burying it. The wasp larva feeds on the paralyzed tarantula which may remain alive for several months while being consumed.

Tarantulas have several defensive strategies that are employed against their enemies (including humans that molest them). First, an aggravated spider will throw itself back on its haunches, thus elevating its cephalothorax and exposing its large fangs. If the harassment persists, the spider will attempt to bite its adversary.

Another deterrent to potential predators are specialized hairs on the top rear of the animal's abdomen. These are called urticating hairs that contain venom. When molested, the spider elevates its abdomen slightly and employs its hind legs to brush these hairs rapidly from the abdomen. The action of the hind legs create a small cloud of extremely fine hairs, which cause a severe irritation when they contact mucous membranes of mammals, including humans.