Aphonopelma chalcodes

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Geographic Range

Desert tarantulas, Aphonopelma chalcodes, are common throughout the Southwestern United States, especially Arizona, New Mexico, and Southern California. (Milne and Milne, 1980)

Habitat

Aphonopelma chalcodes often resides in desert soil. It makes its home in burrows by digging itself under stones or by utilizing burrows discarded by rodents. It may live in the same burrow for decades. Since it lives in the desert, A. chalcodes is acclimated to harsh weather conditions. It does not require much water to survive, and can therefore survive in the extreme heat of the desert. (Miller, 1988)

Physical Description

While sexual dimorphism is apparent in adult A. chalcodes, it is not as drastic as seen in other species. Males have a diameter of 49 to 61 mm, whereas females range from 49 to 68 mm, with a leg span of approximately 98 mm. Desert tarantulas, like other tarantula species, have a body covered entirely with hair. Like all spiders, they are divided into two body segments: the cepholothorax and the abdomen. The cepholothorax is gray to dark brown and the abdomen is dark brown to black. Iridescent hair forms a pad below the tip of each of the eight legs (Milne and Milne, 1980). Tarantulas inject poison into their victims by biting them with fangs on the end of the chelicerae (Jackman, 1997). (Jackman, 1997; Milne and Milne, 1980)

  • Sexual Dimorphism
  • female larger

Development

When young A. chalcodes emerge from an egg, they all resemble females (Milne and Milne, 1980). It is not until later that sexual differentation occurs. Most spiderlings do not survive to reach sexual maturity (Jackman, 1997). They are either eaten by predators or do not find enough food to survive. (Jackman, 1997; Milne and Milne, 1980)

Reproduction

The male emerges from its burrow at sunset and then again near dawn. A male tries to maintain contact with the female, and if she pulls away, he will actively pursue her.

Males have two specialized claws that are shaped like syringes on the ends of its two pedipalps. Male A. chalcodes weave a purse to hold the sperm, which he then loads into the specialized claws. Females have two pouches on the abdomen that are designed to hold the sperm sacks. Sperm sacs can be stored for weeks or months in the female's abdomen until she is ready to lay her eggs. As a female lays her eggs, she bathes each egg in the sperm (Miller, 1988). She weaves a silken sheet and lays up to 1,000 eggs on it. After laying all her eggs, she weaves another sheet, covers the eggs, and then seals the edges. After making this egg sac, a female carries it up to the edge of her burrow to warm it in the sun. Females guard their egg sac until the eggs hatch in up to 7 weeks (Miller, 1988). Three to six days after hatching, the young leave the nest and venture out on their own. (Miller, 1988)

  • Breeding season
    June through December
  • Range number of offspring
    100 to 1000
  • Average number of offspring
    600
  • Average gestation period
    7 weeks
  • Range
    3 to 6 days
  • Range time to independence
    3 to 6 days
  • Range age at sexual or reproductive maturity (female)
    8 to 10 years
  • Range age at sexual or reproductive maturity (male)
    8 to 10 years

Females care for their offspring in a number of ways. In addition to making a safe place for the eggs to hatch, and provisioning those eggs with nutrients, females actively help the eggs incubate by keeping them warm in the sun. Presumably, the female provides protection for the young spiderlings as they live in and around her burrow until they are three to six days old. (Miller, 1988)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • protecting
      • female

Lifespan/Longevity

Male and female desert tarantulas have very different life expectancies. While it takes approximately 8 to 10 years to become sexually mature for both sexes (Miller, 1988), males, after molting for the last time, live for approximately 2 to 3 months. Females, however, continue to molt (shed their exoskeleton as they grow), and may live for up to 20 years. In captivity, females have been known to live for 25 years (Milne and Milne, 1980). (Miller, 1988; Milne and Milne, 1980)

  • Range lifespan
    Status: captivity
    20 (high) years

Behavior

Desert tarantulas are reclusive, nocturnal spiders. They usually hide in their burrows, under rocks, or in abandoned holes during the daylight hours (Milne and Milne, 1980). They hide because they are more vulnerable to predators such as birds and snakes during the day; additionally, their prey are also mainly nocturnal. Between June and December, males can be seen between twilight and sunrise actively searching for females (Miller, 1988). (Miller, 1988; Milne and Milne, 1980)

Communication and Perception

Aphonopelma chalcodes is a solitary creature which lives the majority of its life alone. It makes no sounds, and since tarantulas have poor vision, this species communicates with the outside world and the opposite sex primarily by touch. (Miller, 1988). (Miller, 1988)

Food Habits

Aphonopelma chalcodes spends much of the day hiding in its burrow. When the sun sets, it emerges and begins to search for food.

Foods eaten: lizards, crickets, beetles, grasshoppers, cicadas and caterpillars. (Safra, 1998)

  • Animal Foods
  • reptiles
  • insects

Predation

Humans pose no real threat to desert tarantulas at this time, and A. chalcodes has few natural predators. Only birds and two parasitic insect species (a fly and a tarantula wasp) have been recorded as killing these spiders. When disturbed, desert tarantulas maneuver to face the threat, raise up on their hind legs, and stretch their front legs in a threatening posture. Aphonopelma chalcodes may also rapidly brush the top of its abdomen with its hind legs, which dislodges urticating hairs that can irritate the eyes or skin of an attacker (Jackman, 1997). These poisonous hairs can cause rashes or even partial blindness in the attacker (Miller, 1988). (Jackman, 1997; Miller, 1988)

  • Known Predators

Ecosystem Roles

These spiders presumably impact insect population through their predatory behaviors. As a possible prey species, A. chalcodes may have some positive influence on the populations of its predators and parasites. (Jackman, 1997; Miller, 1988)

Economic Importance for Humans: Positive

Aphonopelma chalcodes has little economic value to humans. It is sometimes sold as a pet, due to its gentle nature and easy maintenance (Miller, 1988). Desert tarantulas also control pests by eating beetles, grasshoppers, millipedes, and other spiders (Miller, 1988). (Miller, 1988)

  • Positive Impacts
  • pet trade
  • controls pest population

Economic Importance for Humans: Negative

Aphonopelma chalcodes does not have a great negative impact on humans. Although its bite is painful, it is not highly poisonous. The venom is similar to that of a mosquito or a bee sting. (Miller, 1988)

  • Negative Impacts
  • injures humans

Conservation Status

Aphonopelma chalcodes is not endangered in any way.

Other Comments

Aphonopelma chalcodes is often a victim of parasitism. A species of fly lays its eggs on the tarantula's back, and when the larvae hatch, they devour the tarantula. A species of wasp, known as tarantula hawks, attack these tarantulas, and if successful, inject their victim with poison and paralyze it. The wasp then drags the tarantula back to its nest and places it next to its eggs. The tarantula can often live for a few months in this paralyzed state, until the eggs hatch and then eat the tarantula. (Miller, 1988)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Ben Craighead (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Jackman, J. 1997. A Field Guide to Common Texas Insects. Houston, Texas: Gulf Publishing.

Miller, G. 1988. Texas Monthly Field Guide to Wildlife in Texas and the Southwest. Austin, Texas: Texas Monthly Press.

Milne, L., M. Milne. 1980. The Audobon Society's Field Guide to North American Insects and Spiders. New York, New York: Alfred A. Knopf.

Safra, J. 1998. The New Encyclopedia Britannica Volume II, 15th Edition. Chicago, Illnois: