Family Theraphosidae — New World species
New World tarantulas are native to the Americas, occupying diverse habitats spanning tropical rainforests, cloud forests, semi-arid scrublands, deserts, and high-elevation mountainous regions up to 4,000 metres. Within the family Theraphosidae — approximately 1,164 species across 186 genera — New World species represent a large and ecologically diverse subset.
The defining evolutionary adaptation of New World tarantulas is their possession of urticating hairs — specialized, barbed microscopic setae on the dorsal and posterior surface of the abdomen. Found in approximately 90% of New World species and absent in all Old World tarantulas, these hairs are the primary defence mechanism. When threatened, a tarantula rapidly rubs its back legs across its abdomen, flicking a cloud of barbed hairs toward a perceived threat. The hairs cause irritation to skin, mucous membranes, and eyes.
Tarantulas are measured by their Diagonal Leg Span (DLS) — the distance from the tip of the front-left leg to the tip of the back-right leg. Enclosure sizing is based on DLS and species type.
| Species Type | Floor Space (L×W) | Height | Substrate Depth |
|---|---|---|---|
| Terrestrial / Burrowing Brachypelma, Grammostola, Aphonopelma | 3–4× DLS | 1–1.5× DLS | 1.5–2× DLS |
| Arboreal Avicularia | 2–3× DLS | 3–4× DLS | 1–1.5× DLS |
Enclosure security is non-negotiable. A tarantula can push through surprisingly small gaps — ensure the lid locks or seals well, and inspect regularly for wear.
Use a substrate that holds moisture without becoming waterlogged:
Coconut husk / Eco-Earth — excellent for most terrestrial species. Holds shape for burrowing.
Topsoil / peat mix — good for established burrowers; compacts well to form stable tunnel walls.
Aspen shavings — only for arid-preferring species. Does not hold humidity.
For terrestrial species, fill the enclosure to 1.5–2× the spider's body length in depth. Leave adequate headroom above the substrate — a fall from a fully stretched enclosure height can be fatal, especially for heavy-bodied tarantulas.
| Parameter | Target Range | Notes |
|---|---|---|
| Temperature | 70–80°F (21–27°C) | Room temperature is usually sufficient — no heat lamp needed |
| Humidity — Tropical species | 65–80% RH | Moist substrate, water dish, cross-ventilation |
| Humidity — Arid species | 40–55% RH | Dry substrate, water dish, good airflow |
| Maximum | 85°F (29°C) | Temperatures above this can be fatal |
Create a moisture gradient rather than a uniformly wet or dry enclosure — one area slightly damp, most of the enclosure dry, with a water dish accessible at all times. This allows the tarantula to self-regulate.
New World tarantulas are generalist ambush predators in the wild. In captivity, gut-loaded crickets, Dubia roaches, and mealworms are the standard prey items. Prey should be sized no larger than the tarantula's abdomen.
| Spider Size | Prey Type | Frequency |
|---|---|---|
| Spiderling (under 1") | Pre-killed pinhead crickets or fruit flies | Every 4–5 days |
| Juvenile (1–3") | Small crickets, small roaches | Every 5–7 days |
| Sub-adult / Adult (3"+) | Adult crickets, Dubia roaches | Every 7–14 days |
Remove uneaten prey within 24 hours — live prey can stress or injure a tarantula, particularly during or around a moult. Never leave live crickets in an enclosure unattended overnight.
Moulting (ecdysis) is how tarantulas grow. The spider sheds its entire exoskeleton — including the lining of its fangs, book lungs, and urticating hair patch. It is the most vulnerable period of a tarantula's life.
Pre-moult signs: Abdomen darkens (spider is building new exoskeleton beneath), food refusal, reduced activity, possible webbing over the enclosure entrance.
During moult: The spider will flip onto its back. This is completely normal — do not intervene. A healthy moult typically completes in 15 minutes to a few hours. Remove all live prey immediately.
Post-moult: Do not offer food for at least 1–2 weeks after moulting. The new exoskeleton needs time to harden (sclerotise) fully. Fangs are white immediately after moulting and gradually darken to black as they harden.
New World tarantulas can be handled, but handling carries risk — primarily to the spider, not the keeper. A fall from even a few inches can rupture the abdomen of a heavy-bodied tarantula, which is almost always fatal.
If you choose to handle: sit on the floor, keep the spider close to a flat surface, move slowly, and never reach from above (this mimics a predator strike). Wash hands before and after.
Dehydration: A shrivelled, wrinkled abdomen is the most common health issue in captivity. Ensure the water dish is always full and consider lightly wetting one corner of the substrate to create a moisture gradient. A dehydrated tarantula typically recovers within days of access to water.
Failed moult: If a tarantula cannot complete its moult within a few hours and is visibly struggling, this is a moult emergency. Carefully mist the substrate to increase humidity. Do not attempt to help the spider out of its old exoskeleton unless the spider has been stuck for 12+ hours and is visibly exhausted — intervention risks tearing limbs.
Mites: Small white or red dots moving through the substrate or on the spider. Remove the tarantula to a clean enclosure, clean the old enclosure thoroughly with hot water (no chemicals), and replace all substrate. Grain mites are usually a sign of too-wet conditions or old prey in the enclosure.
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