Chilobrachys

Chilobrachys Karsch, 1891 is an Asian genus of medium-bodied terrestrial-to-semi-arboreal theraphosids in the subfamily Selenocosmiinae, distributed across South Asia and Southeast Asia from the Indian Western Ghats and adjacent Sri Lanka through Myanmar, Thailand, southern China, peninsular Malaysia, and into the islands of the Greater Sunda Shelf. The genus has had an unusually active recent descriptive history: long stable at roughly a dozen valid species through the 20th century, the Thai fauna alone has produced multiple high-profile new descriptions in the 2020s — most prominently C. natanicharum Songsangchote, Sippawat & Khaikaew, 2023 (the "Electric Blue Tarantula," described from Thai mangroves and the subject of substantial international press coverage in the year of description) — and the body of undescribed Thai trade forms entering the European and US hobby continues to outpace formal description by a wide margin.

Members of the genus are obligately fossorial in most species, with the subset of arboreal-and-mangrove specialists (most notably C. natanicharum) being the diagnostic exception rather than the rule. The standard Chilobrachys habit is a deep silk-lined burrow combined with extensive surface webbing extending well above the substrate — the genus is among the heaviest webbers in the Asian Selenocosmiinae and constructs more visible surface silk than the comparable Cyriopagopus and Selenocosmia. Adult coloration ranges across the genus from the muted fawns and chocolates of the Burmese and Indian fauna (C. dyscolus, C. fimbriatus) through bronze-to-violet sheens on Western Ghats material to the saturated electric-blue iridescence of C. natanicharum and the orange-saturated Thai trade phenotypes that may ultimately resolve into one or several formally described species. As with all Old World theraphosids, no urticating setae are produced; defense is purely flight-and-bite, with a fast retreat into the surface webbing or burrow as the dominant first response and a willing defensive bite as the secondary response when cornered.

Behaviorally Chilobrachys are markedly defensive even by Asian Selenocosmiinae standards. Threat displays are common and brief, retreat speed is high, and bite-readiness when persistently cornered is among the highest in the international hobby — the genus is routinely categorized as advanced and is not appropriate for keepers without substantial Old World terrestrial-fossorial experience. Venom is moderate-to-strong by Asian standards across documented species, with localized pain, swelling, and occasional muscle cramping reported in bite literature; no medically significant systemic envenomation is reliably documented but the upper-end Chilobrachys bite is materially more uncomfortable than the comparable Pterinochilus or Heteroscodra envenomation. Captive husbandry expects 6–8 in of compactable substrate to support deep burrowing, multiple anchor points and substrate-surface architecture (cork bark, slabs, low branches) to accommodate the heavy surface webbing the genus expects, mid-70s to low-80s °F across most of the genus's range, and moderate-to-higher humidity (~70–80%) maintained primarily through a moist substrate base with adequate cross-ventilation. Sustained low humidity in undersized enclosures is the most consistent cause of failed long-term keeping. No Chilobrachys species is currently CITES-listed; conservation pressure is meaningful through habitat loss to agricultural conversion and (in the Thai mangrove specialist C. natanicharum) coastal development.

Chilobrachys dyscolus “Blue”

Vietnam Blue Earth Tiger

Photo: Luxe Inverts

Field Note

The “Vietnam Blue” form circulates in the hobby under the working label Chilobrachys dyscolus “Blue”, though its taxonomic status is unresolved — recent revisions of Asian Chilobrachys suggest it is more likely an undescribed species (often listed as Chilobrachys sp. “Vietnam Blue”) rather than a true conspecific of Karsch’s 1891 Burmese type. Adults develop a pronounced metallic cobalt-to-electric-blue sheen across the legs and carapace under proper lighting, with darker velvety pile elsewhere — a striking departure from the muted fawn-to-tan dorsum of authenticated Burmese C. dyscolus. Behaviorally it is a textbook Selenocosmiinae fossorial: heavy webber, deep burrower, and famously fast.

Range

Reported from Vietnam (with adjacent occurrences attributed to southern China and northern Laos) in lowland tropical and monsoon forest habitats.

Lifestyle

Terrestrial and obligately fossorial; one of the heaviest webbers in the genus. Constructs silk-lined burrows with extensive surface webbing radiating across substrate, decor, and enclosure walls.

Adult Size

Medium-large; females typically 5–6 in diagonal leg span. Metallic cobalt-blue iridescence on legs and carapace; heavy-bodied, compact build with dark velvety abdomen.

Difficulty

Advanced

Temperament

Defensive Old World temperament; ready threat display, exceptional speed on substrate, and quick to deliver a defensive bite. No urticating setae. Venom considered moderate-to-potent by Asian standards — bite reports note prolonged cramping and localized pain.

Habitat

Vietnamese and Indochinese lowland tropical forest. Captive setup expects 6–8 in of compactable substrate for deep burrowing, multiple anchor points for surface webbing, mid-70s to low-80s °F, and moderate-to-higher humidity (~70–80%) with strong cross-ventilation to prevent stagnation.

Selenocosmiinae Fossorial / heavy webber No urticating setae Vietnamese / Indochinese Metallic blue form

Chilobrachys sp. “Aladdin”

Blue Dream Earth Tiger

Photo: Luxe Inverts

Field Note

Circulating in the hobby as Chilobrachys sp. “Aladdin” — and often marketed under the trade name “Blue Dream” — this is an undescribed Thai species named for its hobby line rather than any formal taxonomy. Like the broader wave of recently recognized Thai Chilobrachys (such as C. natanicharum), it is best treated as Chilobrachys sp. pending formal description. Spiderlings present in muted earth tones, while maturing specimens develop a cool blue-to-violet iridescence across the legs and carapace under direct light, set against a dark, velvety body. Behaviorally it is a textbook Selenocosmiinae fossorial: a prodigious webber, deep burrower, and famously fast.

Range

Thailand (Southeast Asia), in lowland tropical and monsoon forest. Exact locality is undocumented in the trade, as with most hobby “sp.” forms.

Lifestyle

Terrestrial and obligately fossorial; one of the heaviest webbers in the genus. Builds silk-lined burrows with extensive surface webbing radiating across substrate, decor, and enclosure walls.

Adult Size

Medium-large; females typically 5–6 in diagonal leg span. Heavy-bodied, compact build with a dark velvety abdomen and blue-to-violet iridescence on the legs and carapace.

Difficulty

Advanced

Temperament

Defensive Old World temperament; ready threat display, exceptional speed on substrate, and quick to deliver a defensive bite. No urticating setae. Venom considered potent by Asian standards — bite reports for the genus note prolonged cramping and localized pain.

Habitat

Thai lowland tropical / monsoon forest. Captive setup expects 6–8 in of compactable substrate for deep burrowing, multiple anchor points for surface webbing, mid-70s to low-80s °F, and moderate-to-higher humidity (~70–80%) with strong cross-ventilation to prevent stagnation.

Selenocosmiinae Fossorial / heavy webber No urticating setae Thai / undescribed sp. Blue iridescent form

Chilobrachys sp. “Siam Orange”

Siam Orange / Thailand Orangesicle

Photo: Luxe Tarantulas

Field Note

“Siam Orange” is a hobby trade name rather than a valid scientific designation: the animal is an undescribed species of Chilobrachys Karsch, 1892 (Theraphosidae: Selenocosmiinae) and does not yet appear in the World Spider Catalog under any binomial. It circulates alongside other unresolved Thai “orange” forms — “Thailand Orange,” “Orangesicle,” and “Uthai Thani Orange” — whose mutual relationships and specific identities are unconfirmed. Chilobrachys is an Asian genus of roughly 30 currently recognized species ranging across Indochina, India, Sri Lanka, and southern China. Its members are diagnosed by a well-developed stridulating organ — thorn-like “strikers” on the chelicerae working against one to three rows of clavate setae (bacillae, the “lyra”) on the maxillae — which produces an audible hiss in defense, and, like all Old World theraphosids, they lack urticating setae. The genus is overwhelmingly brown or blue, so the warm copper-to-tangerine tones of this form are unusual and account for much of its appeal among keepers.

Range

Thailand. The genus ranges across Indochina, India, Sri Lanka, and southern China; this undescribed form is attributed in the trade to central/western Thailand (the “Uthai Thani” tag points to that province), but as an undescribed species its precise wild distribution is undocumented. Inhabits warm, humid forest with deep soil suitable for burrowing. Both wild-collected (WC) and captive-bred animals circulate.

Lifestyle

Terrestrial and obligately fossorial, and an exceptionally heavy webber. Using oversized spinnerets it lines and roofs its burrow and carpets the surrounding surface in dense white silk, transforming an enclosure into a tunnel-and-sheet web fortress. Nocturnal and reclusive; ambushes prey from the burrow mouth or silken apron after dark.

Adult Size

Medium-to-large Asian fossorial; mature females reach roughly 5–6 in diagonal leg span, with males smaller and more gracile. Keepers report fast growth and a strong feeding response. No formal life-history data exist for this undescribed species; keeper-reported female longevity (on the order of 12–20 years) is inferred from related Chilobrachys rather than documented.

Difficulty

Advanced

Temperament

Fast, skittish, and readily defensive. As a selenocosmiine it lacks urticating setae, relying instead on bolting into its burrow, stridulating, and — if cornered — a threat posture and bite. No theraphosid venom is lethal to healthy humans, and peer-reviewed envenomation data specific to Chilobrachys are sparse; however, bites from Old World theraphosids are reported to cause significant local pain and, in some Asian genera, systemic effects such as muscle cramping, so the genus is treated as having medically significant venom. Not a handling species; maintain with the spider secured in its retreat and a clear escape plan.

Habitat

Warm, humid Southeast Asian forest floor. Captive setup expects 6–7 in of deep, evenly moist (not waterlogged) substrate so it can excavate, a pre-started burrow or cork tube, temperatures of about 75–82 °F (24–28 °C), and 70–80% humidity maintained by dampening the lower substrate plus cross-ventilation. Provide a shallow, always-available water dish once past the early sling stage and expect heavy webbing that obscures the enclosure.

Selenocosmiinae Fossorial Heavy webber Old World (no urticating setae) Stridulates Medically significant venom Undescribed (sp.) Thailand

Old World · Selenocosmiinae

Chilobrachys sp. "Kaeng Krachan"

Kaeng Krachan

Photo: Luxe Tarantulas

Field Note

A dark, velvety earth-tiger from the genus Chilobrachys (Karsch, 1892; family Theraphosidae, subfamily Selenocosmiinae). "Kaeng Krachan" is a hobby and trade locality name borrowed from Kaeng Krachan National Park in Phetchaburi Province, Thailand — it is not a valid binomial and does not appear in the World Spider Catalog under any species name. This animal is an undescribed species (sp.), attributed in the trade to the Kaeng Krachan area of Thailand; wild distribution beyond that attribution should not be overstated. As a Selenocosmiine, it carries the genus's defining stridulating organ: thorn-like "strikers" on the chelicerae rasping against rows of clavate setae (bacillae, or "lyra") on the maxillae to produce an audible hiss. Being Old World, it bears no urticating setae and defends with speed and a bite; its venom is regarded as medically significant, though no theraphosid venom is lethal to a healthy human and peer-reviewed envenomation data for Chilobrachys specifically remain sparse.

Range

Thailand. The genus ranges broadly across Indochina, India, Sri Lanka, and southern China; this undescribed form takes its trade name from Kaeng Krachan National Park (Phetchaburi Province, western Thailand), but as an undescribed species its confirmed wild distribution is undocumented and should not be overstated. Inhabits warm, humid forest with deep soil suitable for burrowing. Both wild-collected (WC) and captive-bred animals circulate.

Lifestyle

Terrestrial and obligately fossorial, and an exceptionally heavy webber. Using oversized spinnerets it lines and roofs its burrow and carpets surrounding surfaces in dense white silk, turning an enclosure into a tunnel-and-sheet web fortress. Nocturnal and reclusive; ambushes prey from the burrow mouth or silken apron after dark.

Adult Size

Medium-to-large Asian fossorial; mature females reach roughly 5–6 in (13–15 cm) diagonal leg span, with males smaller and more gracile. Keepers report fast growth and a strong feeding response. No formal life-history data exist for this undescribed species; keeper-reported female longevity (on the order of 12–20 years) is inferred from related Chilobrachys rather than documented.

Difficulty

Advanced

Temperament

Fast, skittish, and readily defensive. As a selenocosmiine it lacks urticating setae, relying instead on bolting into its burrow, stridulating, and — if cornered — a threat posture and bite. No theraphosid venom is lethal to healthy humans, and peer-reviewed envenomation data specific to Chilobrachys are sparse; however, bites from Old World theraphosids are reported to cause significant local pain and, in some Asian genera, systemic effects such as muscle cramping, so the genus is treated as having medically significant venom. Not a handling species.

Habitat

Warm, humid Southeast Asian forest floor. Captive setup expects 6–7 in of deep, evenly moist (not waterlogged) substrate so it can excavate, a pre-started burrow or cork tube, temperatures of about 75–82 °F (24–28 °C), and 70–80% humidity maintained by dampening the lower substrate plus cross-ventilation. Provide a shallow, always-available water dish once past the early sling stage and expect heavy webbing that obscures the enclosure.

Selenocosmiinae Fossorial Heavy webber Old World (no urticating setae) Stridulates Medically significant venom Undescribed (sp.) Thailand

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Chilobrachys fimbriatus

Chilobrachys fimbriatus

Indian Violet

Photo: Luxe Tarantulas

Field Note

Unlike its undescribed Thai cousins, Chilobrachys fimbriatus Pocock, 1899 is a formally described, valid species — one of the longest-recognized members of an Asian genus (Theraphosidae: Selenocosmiinae) of roughly 30 species spanning Indochina, India, Sri Lanka, and southern China. It is also arguably the genus’s showpiece: a caramel-to-ochre carapace and legs washed in violet sheen, set against a boldly dark-banded, tiger-striped abdomen that makes it instantly recognizable. Like all Chilobrachys, it carries a well-developed stridulating organ — cheliceral “strikers” worked against rows of clavate setae (the lyra) on the maxillae — producing an audible defensive hiss, and like all Old World theraphosids it lacks urticating setae. A prolific silk-layer and reliable captive breeder, it remains one of the most sought-after Asian fossorials in the hobby.

Range

Endemic to western India: coastal Goa and adjacent stretches of the Western Ghats, a monsoon-fed biodiversity hotspot averaging roughly 27 °C with heavy seasonal rainfall. Inhabits warm, humid forest with deep lateritic soil suited to burrowing. Its restricted distribution makes captive-bred stock strongly preferred over wild-collected animals.

Lifestyle

Terrestrial and obligately fossorial, and among the heaviest webbers in the hobby. It lines and roofs a deep burrow and carpets the surrounding surface in dense white sheet silk, converting an enclosure into a tunnel-and-curtain fortress. Nocturnal and reclusive; ambushes prey from the burrow mouth or silken apron after dark.

Adult Size

Medium-to-large Asian fossorial; mature females commonly reach about 5–6 in diagonal leg span (some keepers report up to 7 in), with males smaller and more gracile. Growth is fast and the feeding response is strong. Female longevity is typically cited on the order of 12–15+ years, with males considerably shorter-lived.

Difficulty

Advanced

Temperament

Fast, skittish, and readily defensive. As a selenocosmiine it lacks urticating setae, relying instead on bolting into its burrow, stridulating, and — if cornered — a threat posture and bite. No theraphosid venom is lethal to healthy humans, and peer-reviewed envenomation data specific to Chilobrachys are sparse; however, bites from Old World theraphosids are reported to cause significant local pain and, in some Asian genera, systemic effects such as muscle cramping, so the genus is treated as having medically significant venom. Not a handling species; maintain with the spider secured in its retreat and a clear escape plan.

Habitat

Warm, humid western Indian forest floor. Captive setup expects 6–7 in of deep, evenly moist (not waterlogged) substrate so it can excavate, a pre-started burrow or cork tube, temperatures of about 75–82 °F (24–28 °C), and 70–80% humidity maintained by dampening the lower substrate plus cross-ventilation. Provide a shallow, always-available water dish once past the early sling stage and expect heavy webbing that obscures the enclosure.

Selenocosmiinae Fossorial Heavy webber Old World (no urticating setae) Stridulates Medically significant venom Pocock, 1899 India

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Chilobrachys sp. South Thailand Blue

Chilobrachys sp. “South Thailand Blue”

Blue Dream Earth Tiger

Photo: Luxe Tarantulas

Field Note

“South Thailand Blue” is a hobby trade name, not a valid scientific designation: the animal is an undescribed species of Chilobrachys Karsch, 1892 (Theraphosidae: Selenocosmiinae) and does not appear in the World Spider Catalog under any binomial. It should not be confused with Chilobrachys natanicharum Chomphuphuang et al., 2023 — the formally described “Electric Blue” tarantula reported from mangrove and evergreen forest in Phang Nga province, southern Thailand (ZooKeys 1180: 105–128) — though the relationship of the various Thai “blue” trade forms to that species and to one another remains unresolved. Chilobrachys is an Asian genus of more than 30 valid species (type species C. nitelinus Karsch, 1892, Sri Lanka) ranging across Indochina, India, Sri Lanka, and southern China, diagnosed by a well-developed stridulating organ on the prolateral maxillae and chelicerae; like all Old World theraphosids it lacks urticating setae. While the genus runs heavily to brown, this form is a standout: royal-blue legs set against an iridescent violet-washed abdomen.

Range

Southern Thailand. As an undescribed species its precise wild distribution is undocumented; field reports describe it occupying deep, self-silked retreats in rock crevices and cavities as well as burrows in lower ground, favoring fully shaded, heavily overgrown humid forest. Both wild-collected (WC) and captive-bred animals circulate; captive-bred stock is preferred.

Lifestyle

Terrestrial and fossorial — somewhat opportunistic in retreat choice, silking out rock cavities where available — and an exceptionally heavy webber. It lines and roofs its retreat and carpets the surrounding surface in dense white sheet silk, converting an enclosure into a tunnel-and-curtain fortress. Nocturnal and reclusive; ambushes prey from the retreat mouth or silken apron after dark.

Adult Size

Large Asian fossorial; mature females reach roughly 5–6 in diagonal leg span, with males smaller and more gracile. Keepers report fast growth, a strong feeding response, and bolder surface behavior once spiders pass about 5 in. No formal life-history data exist for this undescribed species; keeper-reported female longevity (on the order of 12–20 years) is inferred from related Chilobrachys rather than documented.

Difficulty

Advanced

Temperament

Fast, skittish, and readily defensive, though keepers report it settles somewhat once large and established. As a selenocosmiine it lacks urticating setae, relying instead on bolting into its retreat, stridulating, and — if cornered — a threat posture and bite. No theraphosid venom is lethal to healthy humans, and peer-reviewed envenomation data specific to Chilobrachys are sparse; however, bites from Old World theraphosids are reported to cause significant local pain and, in some Asian genera, systemic effects such as muscle cramping, so the genus is treated as having medically significant venom. Not a handling species; maintain with the spider secured in its retreat and a clear escape plan.

Habitat

Warm, humid southern Thai forest floor in deep shade. Captive setup expects 6–7 in of deep, evenly moist (not waterlogged) substrate so it can excavate, a pre-started burrow or cork tube plus hard anchor points for webbing, temperatures of about 75–82 °F (24–28 °C), and 70–80% humidity maintained by dampening the lower substrate plus cross-ventilation. Provide a shallow, always-available water dish once past the early sling stage and expect heavy webbing that obscures the enclosure.

Selenocosmiinae Fossorial Heavy webber Old World (no urticating setae) Stridulates Medically significant venom Undescribed (sp.) Thailand