Atomic Dwarf Tarantula (Aphonopelma atomicum)

ReptileCommunity · October 11, 2026, 1:58pm

Atomic Dwarf Tarantula (Aphonopelma atomicum)

Comprehensive Species Care Guide — The Vivarium Vault

Quick Facts

Category	Information
Scientific name	Aphonopelma atomicum
Scientific authority	Hamilton, 2016
Common name	Atomic Dwarf Tarantula (descriptive name)
Family	Theraphosidae
Species group	Paloma species group
Native distribution	Southern Nevada and eastern California, USA
Known region	Amargosa Desert, Amargosa Range and surrounding foothills
Ecoregion	Mojave Basin and Range
Recorded elevation	Approximately 850–1,220 m
Adult size	Miniaturised; among the smallest US tarantulas
Lifestyle	Terrestrial, burrowing
Characteristic burrow	Entrance often surrounded by a soil-and-silk turret
Likely breeding season	October–November
Diet	Small terrestrial invertebrates
Urticating hairs	Present
Venom	Present
Cohabitation	Solitary
Experience level	Advanced
Captive availability	Uncommon; verify provenance
Principal care priorities	Secure housing, stable burrowing substrate, moisture gradient and appropriately sized prey

Evidence distinction: The taxonomy, recorded distribution, elevation, turreted burrows and probable mating season are documented in the original species description. Captive temperature ranges, enclosure dimensions, feeding schedules and longevity are not supported by controlled species-specific husbandry studies.

1. Species Overview

The Atomic Dwarf Tarantula (Aphonopelma atomicum) is a remarkably small terrestrial tarantula native to the Mojave Desert region of the south-western United States.

It was formally described by Chris A. Hamilton in 2016 during a major revision of the North American genus Aphonopelma.

The species is particularly interesting because of its small adult size, restricted documented distribution and distinctive burrow entrances.

Unlike the much larger tarantulas commonly associated with desert habitats, A. atomicum is a miniaturised species.

Its name refers to the former Nevada Test Site, where specimens were collected, and the atomic-testing history of the region.

The original description also notes the irony of the name, given that the species is among the smallest tarantulas known from the United States.

Although it inhabits desert country, this does not mean that it should be exposed to intense heat or maintained on completely dry substrate.

Its underground retreat provides a protected microhabitat that can differ substantially from exposed surface conditions.

In captivity, the principal aim is to provide an appropriately scaled, escape-proof enclosure with sufficient substrate to permit burrowing, reliable access to water and a moderate thermal environment.

Because very little species-specific captive husbandry information is available, this guide uses conservative recommendations and identifies important areas of uncertainty.

2. Taxonomy and Scientific Identification

Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Infraorder: Mygalomorphae
Family: Theraphosidae
Genus: Aphonopelma
Species: Aphonopelma atomicum

Original description

Aphonopelma atomicum was described by Hamilton in 2016.

The description appeared in the comprehensive revision of United States Aphonopelma by Hamilton, Hendrixson and Bond.

Species group

It belongs to the Paloma species group.

Closely related species

Molecular analyses place it close to several other small-bodied Aphonopelma, including:

Aphonopelma mojave
Aphonopelma icenoglei
Aphonopelma prenticei
Aphonopelma joshua

Similarity to other species

Small-bodied Aphonopelma can be difficult to distinguish by appearance alone.

Identification methods

The original taxonomic treatment uses a combination of:

Morphological characteristics.
Molecular evidence.
Geographical distribution.
Comparison with related species.

Colouration

Colour should not be considered diagnostic by itself.

Provenance

Accurate provenance is important, particularly because the species may occur near other closely related tarantulas.

Sex determination

Sex determination can be attempted using suitable moults, but the small size makes examination difficult.

Breeding precaution

Do not breed individuals of uncertain identity or combine unrelated locality records without appropriate documentation.

3. Natural Distribution and Ecology

Geographic distribution

Aphonopelma atomicum is known from a relatively small number of specimens collected around the Amargosa Desert.

Its documented distribution includes:

Southern Nye County, Nevada.
South-eastern Inyo County, California.
The Amargosa Range.
The Nevada Test Site region.

Ecoregion

The species inhabits the Mojave Basin and Range ecoregion.

Elevation

Published specimen records occur between approximately 850 and 1,220 metres above sea level.

Habitat characteristics

The region contains arid valleys, rocky foothills, desert slopes and sparse vegetation.

However, precise microhabitat preferences should not be assumed from regional climate alone.

Natural burrows

One of the most distinctive documented features is the burrow entrance.

The original species description reports that entrances are commonly surrounded by a small turret formed from excavated soil and silk.

This structure may help define and protect the entrance, although its precise function has not been experimentally established for this species.

Importance of substrate

This natural behaviour supports providing a substrate that can hold its shape.

Associated species

A. atomicum may occur in the same general areas as the much larger Aphonopelma iodius.

It may also occur near populations of A. prenticei.

Seasonal reproductive activity

The original description suggests that mating most likely occurs during daylight hours in October and November.

This is a field-based interpretation rather than a validated captive breeding schedule.

Environmental implications

Captive housing should support burrowing and protected microclimates rather than simply copying exposed desert surface temperatures.

4. Adult Size, Growth and Lifespan

Adult size

Aphonopelma atomicum is one of the smallest tarantulas documented in the United States.

Measurements

The original scientific treatment includes measurements of diagnostic specimens.

Because adult dimensions vary, enclosure selection should be based on the individual spider rather than an unsupported universal leg-span figure.

Growth rate

Reliable species-specific captive growth data are unavailable.

Female lifespan

A verified maximum female lifespan has not been established.

Male lifespan

As with many tarantulas, mature males generally have shorter remaining lifespans than females.

Growth monitoring

Record:

Moulting dates.
Feeding responses.
Abdominal condition.
Behavioural changes.
Development of mature male structures.

Avoid assumptions

Do not apply lifespan or growth-rate figures from large Aphonopelma species without evidence.

5. Housing and Enclosure Requirements

Housing should reflect the spider’s miniaturised size and documented burrowing behaviour.

Adult enclosure dimensions

For a small adult, a practical starting enclosure is:

6 × 6 × 8 inches (15 × 15 × 20 cm)

An alternative providing additional floor space is:

8 × 8 × 8 inches (20 × 20 × 20 cm)

These dimensions are practical recommendations rather than scientifically validated minimum requirements.

Floor space

Provide enough horizontal room for movement, retreat construction, feeding and access to water.

Substrate depth

A practical starting depth is:

4–5 inches (10–13 cm)

This allows meaningful excavation while maintaining a relatively low fall height above the substrate.

Burrow construction

Provide a small starter excavation beneath cork bark or another stable shelter.

Soil-and-silk turrets

If the spider constructs a turret around its entrance, leave it undisturbed.

Do not remove it merely for cosmetic reasons.

Enclosure security

Very small tarantulas can escape through narrow gaps.

Check:

Lid fittings.
Ventilation holes.
Door gaps.
Cable openings.
Sliding-door tracks.
Feeding access points.

Ventilation

Provide secure, suitably fine ventilation openings.

Fall prevention

Keep the unobstructed height above the substrate low.

Enclosure materials

Suitable plastic, acrylic or glass containers may be used.

Furnishing stability

Secure heavier decorations against collapse during excavation.

Spiderling housing

Spiderlings require appropriately scaled secure containers.

Provide:

Compactable substrate.
A small retreat.
Fine ventilation openings.
Carefully managed moisture.
Tiny suitable prey.

Juvenile housing

Increase enclosure size gradually.

Subadult housing

Provide sufficient floor space and substrate depth for normal excavation.

Individual housing

Keep all specimens separately.

6. Substrate and Burrowing

Substrate design is especially important for this species.

Natural evidence

Wild burrow entrances may have turrets constructed from excavated soil and silk.

Suitable substrate materials

Reptile-safe topsoil.
Soil-based terrestrial tarantula substrate.
Topsoil blended with coco coir.
Other clean, compactable mixtures.

Structure

Lightly compact the substrate during setup.

Depth

Approximately 4–5 inches is a practical adult starting point.

Moisture

Maintain a modest moisture gradient.

Surface conditions

Allow substantial surface areas to remain relatively dry.

Lower substrate

A small portion may remain slightly moist.

Starter burrow

Create a shallow excavation beneath a stable hide.

Avoid collapse

Do not use excessively loose substrate that repeatedly collapses.

Avoid contamination

Do not use fertilised compost, pesticide-treated soil or strongly scented wood products.

Burrow preservation

Avoid unnecessary excavation of established retreats.

7. Furnishings and Environmental Enrichment

The enclosure should support natural behaviour without introducing hazards.

Suitable furnishings

Small cork bark hides.
Ground-level shelters.
Fine leaf litter.
Stable low stones.
A shallow drinking-water dish.

Retreat construction

Allow the spider to modify its shelter.

Turret preservation

Do not destroy soil-and-silk structures during routine maintenance.

Environmental choice

Provide more than one sheltered location where space permits.

Stability

Secure heavier furnishings.

Avoid climbing hazards

Tall branches and elevated platforms are unnecessary.

8. Temperature and Heating

The Mojave Desert experiences extreme environmental variation.

However, the temperatures inside underground retreats may differ considerably from exposed surface conditions.

Provisional captive starting temperatures

Condition	Suggested temperature
General daytime	21–25°C
Slightly warmer area	Up to approximately 26°C
Cooler retreat	Approximately 20–22°C
Night-time	Approximately 18–21°C

These figures are cautious husbandry recommendations, not experimentally established species-specific preferences.

Avoid extreme heat

Do not expose the enclosure to the extreme surface temperatures recorded in desert habitats.

Heating in Ireland

Supplementary heating may be needed during colder months.

Preferred approach

Stable ambient room heating is generally easier to control than concentrated localised heat.

Thermostatic control

Use appropriate control equipment with supplementary heating.

Under-enclosure heating

Avoid heating directly beneath deep substrate.

Temperature monitoring

Measure actual enclosure temperatures.

Seasonal variation

Modest seasonal variation may occur naturally in a suitable room.

Do not impose severe winter cooling without species-specific evidence.

9. Lighting and UVB

Specialist UVB lighting is not routinely required.

Day-night cycle

Provide a normal light-dark rhythm.

Ambient lighting

Indirect room lighting is generally sufficient.

Display lighting

Low-output LEDs may be used if they do not cause overheating.

Night-time

Provide darkness.

Avoid

Do not use intense basking lamps.

10. Humidity, Ventilation and Hydration

A scientifically validated relative humidity target is unavailable.

Drinking water

Provide a small, stable drinking-water dish.

Moisture gradient

Maintain slightly moist substrate in one lower area.

Surface

Allow substantial surface areas to remain relatively dry.

Ventilation

Provide effective airflow.

Spiderlings

Small containers can dry rapidly and require careful moisture monitoring.

Misting

Routine heavy misting is unnecessary.

Warning signs

Persistent condensation, mould or waterlogged substrate indicate unsuitable conditions.

Observation

Monitor burrow use, feeding, activity and moulting.

11. Feeding and Nutrition

The Atomic Dwarf Tarantula is a carnivorous predator.

Suitable prey

Small crickets.
Small feeder cockroaches.
Appropriately sized mealworms.
Other suitable captive-bred insects.

Spiderlings

Offer tiny prey or suitable portions of freshly killed feeder insects.

Juveniles

Approximately weekly feeding is a practical starting point.

Adults

Offer appropriately sized prey approximately every 7–14 days initially.

Prey size

Avoid prey that is excessively large relative to the spider.

Adjustments

Modify feeding according to body condition, appetite and moulting.

Burrow feeding

Offer prey near the retreat entrance without repeatedly disturbing the spider.

Uneaten prey

Remove uneaten insects promptly.

Wild insects

Avoid wild-caught feeders because of pesticide and parasite risks.

Vertebrate prey

Vertebrate feeding is unnecessary.

12. Calcium and Vitamin Supplementation

Routine reptile calcium and vitamin dusting is not recommended.

Tarantulas consume whole prey.

Maintain feeder insects under appropriate conditions.

No validated supplementation schedule exists for A. atomicum.

13. Moulting and Growth

Moulting allows the spider to grow and renew its exoskeleton.

Premoult signs

Reduced appetite.
Increased concealment.
Retreat closure.
Reduced activity.
Changes in abdominal appearance.

During moulting

Do not disturb the spider.

A tarantula lying on its back may be moulting normally.

Do not turn it over.

After moulting

Allow the exoskeleton and fangs to harden before feeding.

Small specimens

Because the spider is small, assessing fang hardening may be difficult.

Do not rush feeding.

Complications

Do not forcibly remove retained exoskeleton.

Seek specialist advice where necessary.

14. Urticating Hairs and Defensive Behaviour

Aphonopelma tarantulas possess defensive urticating hairs.

Defensive responses

A disturbed spider may retreat, release hairs, adopt a defensive posture or bite.

Possible effects

Urticating hairs may cause:

Itching.
Skin irritation.
Eye irritation.
Respiratory irritation.

Eye exposure

Do not rub the eye.

Seek prompt medical assessment.

Individual variation

Defensive behaviour varies.

Prevention

Avoid unnecessary handling.

15. Venom and Bite Safety

The species possesses venom-bearing fangs.

Possible effects

Puncture wounds.
Local pain.
Swelling.
Redness.
Individual reactions.

Detailed species-specific clinical evidence is limited.

First aid

Wash a bite wound with clean running water.

Seek medical advice where appropriate.

Severe allergic symptoms or breathing difficulties require urgent medical attention.

16. Handling and Safe Rehousing

Routine handling is not recommended.

Main risks

Escape.
Falls.
Bites.
Urticating-hair exposure.
Unnecessary disturbance.

Rehousing equipment

Use a suitably sized catch cup, soft brush and secure receiving enclosure.

Preparation

Prepare the receiving enclosure before moving the spider.

Transfer

Gently guide the spider into a transfer container.

Burrowed individuals

Avoid forcibly excavating the spider unless necessary.

Escape prevention

Work in a controlled area without accessible gaps or drains.

After transfer

Check all enclosure openings before leaving the spider unattended.

17. Cohabitation

House Atomic Dwarf Tarantulas individually.

Risks

Cannibalism.
Injury.
Competition for retreats.
Feeding interference.
Stress.

Temporary supervised breeding introductions do not justify permanent cohabitation.

18. Cleaning and Routine Maintenance

Daily

Check water, temperature and enclosure security.

After feeding

Remove uneaten prey.

Weekly

Clean the water dish, remove visible waste and inspect for mould.

Periodically

Review substrate condition, ventilation and equipment.

Substrate replacement

Replace contaminated substrate when necessary.

Avoid unnecessary complete enclosure disruption.

Burrow preservation

Avoid destroying established soil-and-silk structures.

19. Common Health Concerns

Dehydration

Ensure access to drinking water and appropriate substrate moisture.

Moulting complications

Incomplete moults can cause serious injury.

Falls

Abdominal injuries may be fatal.

Mites

Not all small organisms in substrate are parasites.

Persistent mites concentrated on the spider require investigation.

Mould

Persistent mould may indicate excessive moisture or inadequate ventilation.

Feeding refusal

Consider premoult, body condition and environmental conditions.

Abnormal posture

Severe leg curling, weakness or unresponsiveness warrants urgent specialist assessment.

Veterinary support

Seek advice from a suitably experienced exotic or invertebrate veterinarian.

20. Quarantine

Maintain new acquisitions separately from established collections.

A precautionary observation period of approximately 60–90 days may be used.

This is not a scientifically validated disease-free interval.

Monitor

Feeding.
Moulting.
Body condition.
Visible mites.
Abnormal behaviour.
Enclosure hygiene.

Equipment

Use separate maintenance equipment where practical.

Provenance

Retain identification and acquisition records.

21. Breeding

Breeding Aphonopelma atomicum requires reliable identification and experience with small terrestrial tarantulas.

Identification

Confirm the identity and provenance of both animals.

Sex determination

Examine a suitable moult where possible.

Mature males

Males develop specialised reproductive structures.

Seasonal activity

The original description suggests mating most likely occurs during daylight hours in October–November.

Pairing

Supervise introductions.

Cannibalism

Females may attack or consume males.

Egg sacs

Successful mating may result in egg-sac production.

Incubation

A validated species-specific captive incubation protocol is unavailable.

Spiderlings

Provide secure accommodation, suitable substrate, carefully managed moisture and appropriately sized prey.

Records

Maintain accurate parentage, pairing and offspring records.

22. Conservation and Responsible Captive Breeding

Aphonopelma atomicum has a restricted documented distribution around the Amargosa Desert and Death Valley region.

Conservation considerations

Its geographical restriction makes accurate identification and provenance important.

Original assessment

The 2016 species description suggested that the species was likely secure.

This is not equivalent to a current formal IUCN assessment.

Habitat pressures

Potential pressures include habitat disturbance and inappropriate collection.

Captive-bred acquisition

Prioritise legally sourced captive-bred individuals with credible provenance.

Wild collection

Do not assume collection is permitted.

Breeding responsibility

Maintain accurate identification and parentage records.

Conservation value

Responsible captive breeding may reduce demand for wild-collected specimens.

However, captive breeding does not replace habitat conservation.

Release

Never release captive tarantulas into the environment.

23. Legal and CITES Information

Current CITES status should be checked against the official CITES Checklist before international trade.

United States

Collection, possession and export requirements may vary by jurisdiction and protected-area status.

European Union

Check applicable wildlife trade, customs and import requirements.

Ireland

Consult the National Parks and Wildlife Service where clarification is required.

Documentation

Retain:

Scientific identification.
Supplier details.
Acquisition date.
Evidence of lawful origin.
Captive-bred records where available.
Relevant permits.
Breeding records.

Important distinction

Absence from CITES does not necessarily mean that collection or international trade is unrestricted.

24. Common Husbandry Mistakes

Confusing Mojave Desert species with Sonoran Desert species.
Using an enclosure intended for a much larger tarantula.
Leaving escape-sized ventilation openings.
Providing excessive enclosure height.
Providing insufficient substrate.
Using substrate that collapses around burrows.
Destroying soil-and-silk turrets during maintenance.
Maintaining permanently wet conditions.
Providing no accessible drinking water.
Overheating a small enclosure.
Heating directly beneath deep substrate.
Offering excessively large prey.
Leaving live prey during moulting.
Disturbing established retreats.
Routine handling.
Communal housing.
Breeding animals of uncertain identity.

25. Husbandry Summary

Requirement	Practical recommendation
Scientific name	Aphonopelma atomicum
Common name	Atomic Dwarf Tarantula
Native range	Southern Nevada and eastern California
Ecoregion	Mojave Basin and Range
Recorded elevation	Approximately 850–1,220 m
Adult size	Miniaturised
Lifestyle	Terrestrial and burrowing
Natural burrow	Soil-and-silk entrance turret
Adult enclosure	Approximately 6 × 6 × 8 inches
Larger enclosure	Approximately 8 × 8 × 8 inches
Substrate depth	Approximately 4–5 inches
Daytime temperature	Approximately 21–25°C
Night-time temperature	Approximately 18–21°C
Moisture	Modest gradient, relatively dry surface
Ventilation	Effective, escape-proof airflow
Water	Small accessible drinking-water dish
Lighting	Normal day-night cycle
UVB	Not routinely required
Diet	Small captive-bred feeder insects
Likely breeding season	October–November
Urticating hairs	Present
Venom	Present
Handling	Not recommended
Cohabitation	Solitary
Experience	Advanced
CITES	Verify current status

26. References and Further Reading

Hamilton, C. A., Hendrixson, B. E. & Bond, J. E. (2016). Taxonomic revision of the tarantula genus Aphonopelma within the United States. ZooKeys, 560, 1–340. Taxonomic revision of the tarantula genus Aphonopelma Pocock, 1901 (Araneae, Mygalomorphae, Theraphosidae) within the United States
World Spider Catalog. Aphonopelma atomicum Hamilton, 2016. Natural History Museum Bern. World Spider Catalog
Integrated Taxonomic Information System. Aphonopelma atomicum, Taxonomic Serial Number 1088709. https://www.itis.gov
Foelix, R. F. Biology of Spiders. General reference for spider anatomy and behaviour.
CITES. Checklist of CITES Species. https://checklist.cites.org
National Parks and Wildlife Service, Ireland. https://www.npws.ie

Evidence Note

The accepted taxonomy, scientific description, Mojave Desert distribution, recorded elevation, small adult body size, soil-and-silk burrow turrets and probable autumn mating activity are supported by the 2016 taxonomic revision.

The enclosure dimensions, temperature ranges, feeding intervals and moisture-management recommendations are provisional captive husbandry guidance.

Detailed species-specific captive longevity, preferred thermal conditions and breeding protocols remain insufficiently documented.

IMPORTANT INFORMATION

This care sheet provides general husbandry guidance and does not replace species-specific research or veterinary advice. Individual requirements may vary.

Always check current legislation governing the acquisition, collection, import, transport, keeping, breeding or sale of reptiles and invertebrates in your jurisdiction.

If you have concerns about an animal’s health or care, consult a suitably experienced exotic or invertebrate veterinarian.

Information correct at the date of publication, subject to subsequent changes in scientific knowledge and legislation.

ReptileCommunity.com | Revised: October 2026