Tarantula — Tarantula is the common name for a group of “hairy” and often very large spiders belonging to the family Theraphosidae, of which approximately 900 species have been identified. Tarantulas hunt prey in both trees and on the ground. All tarantulas can emit silk, whether they be arboreal or terrestrial species. Arboreal species will typically reside in a silken “tube web”, and terrestrial species will line their burrows or lairs with web to catch wandering prey. They mainly eat insects and other arthropods, using ambush as their primary method. The biggest tarantulas can kill animals as large as lizards, mice, or birds. Most tarantulas are harmless to humans, and some species are popular in the exotic pet trade while others are eaten as food. These spiders are found in tropical and desert regions around the world.
The name tarantula comes from the town of Taranto in Italy and was originally used for an unrelated species of European spider. In Africa, Theraphosids are frequently referred to as “baboon spiders”. Asian forms are known as “earth tigers” or “bird spiders”. Australians refer to their species as “barking spiders”, “whistling spiders,” or “bird spiders”. People in other parts of the world also apply the general name “mygales” to Theraphosid spiders.
There are other species also referred to as tarantulas outside this family; the evolution of the name Tarantula is discussed below. This article primarily concerns the Theraphosids.
the tarantula is an invertebrate that relies on an exoskeleton for muscular support. A tarantula’s body consists of two main parts, the prosoma or the cephalothorax (the former is most often used because there is no analogous “head”) and the abdomen or opisthosoma. The prosoma and opisthosoma are connected by the pedicle or what is often called the pregenital somite. This waist-like connecting piece is actually part of the prosoma and allows the opisthosoma to move in a wide range of motion relative to that of the prosom.
The majority of North American tarantulas are brown. Many species have more extensive coloration patterns, ranging from cobalt blue (Haplopelma lividum), black with white stripes (Eupalaestrus campestratus or Aphonopelma seemanni), to metallic blue legs with vibrant orange abdomen (Chromatopelma cyaneopubescens, green bottle blue). Their natural habitats include savanna, grasslands such as the pampas, rainforests, deserts, scrubland, mountains and cloud forests. They are generally divided into terrestrial types that frequently make burrows and arboreal types that build tented shelters well off the ground.
The tarantula’s mouth is located under its chelicerae on the lower front part of its prosoma. The mouth is a short straw-shaped opening which can only suck, meaning that anything taken into it must be in liquid form. Prey with large amounts of solid parts such as mice must be crushed and ground up or predigested, which is accomplished by spraying the prey with digestive juices that are excreted from openings in the chelicerae.
The tarantula’s digestive organ (stomach) is a tube that runs the length of its body. In the prosoma, this tube is wider and forms the sucking stomach. When the sucking stomach’s powerful muscles contract, the stomach is increased in cross-section, creating a strong sucking action that permits the tarantula to suck its liquified prey up through the mouth and into the intestines. Once the liquified food enters the intestines, it is broken down into particles small enough to pass through the intestine walls into the haemolymph (blood stream) where it is distributed throughout the body.
Tarantulas may live for years–most species taking 2 to 5 years to reach adulthood, but some species may take up to 10 years to reach full maturity. Upon reaching adulthood, males typically have but a 1 to 1.5 year period left to live and will immediately go in search of a female with which to mate. It is rare that upon reaching adulthood the male tarantula will molt again. The oldest spider, according to Guinness World Records, lived to be 49 years old.
Females will continue to molt after reaching maturity. Female specimens have been known to reach 30 to 40 years of age, and have survived on water alone for up to 2.5 years. Grammostola rosea spiders are renowned for going for long periods without eating.