Origin And Natural Habitat
The rainforests of Sarawak on the island of Borneo in Malaysian Borneo are the exclusive home of Birupes simoroxigorum — a species endemic to Borneo and found nowhere else on Earth. Sarawak is one of the two Malaysian states on Borneo, a vast island of extraordinary biodiversity where the lowland rainforest is among the most species-rich on the planet. The specific habitat documented for this species is lowland rainforest — the hot, humid, consistently warm forest of Borneo’s lower elevations, where annual rainfall is extremely high, temperatures barely vary between seasons, and the forest floor is a rich, moist environment of decomposing organic matter, root systems, and loose soil.
As a fossorial species that buries itself in this moist lowland forest floor, B. simoroxigorum constructs burrows in the soft, organic-rich substrate of the forest interior — though keeper observation has revealed a more complex lifestyle than a strict fossorial classification suggests. Unlike many other fossorial species, it exhibits burrowing and arboreal tendencies, sometimes utilising vertical retreats in rotting wood or loose substrate, and occasionally spending days visible on the surface in the open — a behavioural flexibility that makes it one of the more unpredictable and interesting fossorial tarantulas to keep.
The species was first described in 2019 — extraordinarily recently for a tarantula that has already become one of the most sought-after species in the hobby — and its introduction into the keeping community was immediately surrounded by controversy, as early specimens were removed from Borneo without Malaysian government permission. That context makes responsible captive-bred sourcing not just preferable but ethically essential for this species.
Scientific Classification
Described by R. Gabriel and D. Sherwood in 2019, Birupes simoroxigorum is a monotypic genus — meaning it is the only species in the genus Birupes, which was erected specifically to accommodate it. The genus and species names are derived from the Iban language of Borneo’s indigenous Dayak people — birupes meaning “blue leg” and simoroxigorum meaning “neon” in Iban, making the scientific name itself a translation of the common name in the indigenous language of the spider’s homeland. This naming decision is a meaningful acknowledgement of the Iban people’s relationship with the Bornean rainforest. The World Spider Catalog and iNaturalist confirm B. simoroxigorum Gabriel & Sherwood, 2019 as the current valid name. Full classification: Kingdom Animalia, Phylum Arthropoda, Class Arachnida, Order Araneae, Infraorder Mygalomorphae, Family Theraphosidae, Genus Birupes, Species B. simoroxigorum Gabriel & Sherwood, 2019.
Species Overview
Few tarantulas in living memory have entered the hobby with the explosive visual impact of Birupes simoroxigorum. From the moment photographs began circulating in 2019, it was considered by some to be the most beautiful spider in the world — a claim that is difficult to dispute when you see the neon blue legs against the creamy brown body in person. It quickly became one of the most desirable species in the hobby and one of the most expensive, with the combination of extreme visual impact, rarity, and the controversy around its initial extraction driving demand well beyond what the small captive breeding population could initially meet. Captive breeding has expanded since those earliest years and specimens are now more available than they were immediately after discovery — though prices remain high. It is an advanced keeper species given its Old World status, defensive temperament, and the specific care requirements of a Bornean lowland rainforest fossorial.
Appearance And Size
The blue is the entire story, and words do not do it justice — but the attempt is worth making. The legs carry a vivid neon blue coloration so bright it appears backlit, contrasting against a creamy brown body that is itself attractive but exists primarily as a canvas to make the blue more dramatic by contrast. The blue is not the subtle iridescent metallic blue of many Old World species — it is an almost impossibly saturated neon quality that makes the spider look artificial in photographs and somehow even more extraordinary in person. The overall palette of bright blue legs and cream-brown body is unlike anything else in the fossorial tarantula world, where colour complexity of this kind has historically been the domain of arboreal species. The colouration deepens and becomes more vivid after each moult, with freshly moulted specimens showing the most saturated blue.
Adult legspan reaches 4 to 5 inches — a compact to medium size that makes the blue colouration feel concentrated rather than spread across a large body. Growth rate is fast relative to many Old World species, which combined with captive breeding expansion means adult specimens are increasingly achievable within a reasonable timeframe.
Housing
A fossorial enclosure with substrate depth as the defining priority, with an important caveat — the species also shows arboreal and surface tendencies that mean a completely bare terrestrial format without any vertical structure misses part of its natural behavioural range. Six to eight inches of substrate for adults provides burrowing depth, while a piece of cork bark or rotting wood positioned vertically gives the spider a structure to retreat into or climb when it chooses surface-level arboreal behaviour. A front-opening enclosure with a secure latching lid is essential given Old World speed. Our best tarantula enclosure guide covers formats appropriate for Old World fossorial species with hybrid burrowing and surface behaviour.
Enclosure’s Decorations
A pre-formed starter burrow angled into the substrate at one corner gives the spider an immediate starting point for deep burrow construction. A piece of cork bark or rotting wood positioned vertically in the substrate — partially buried with the upper portion exposed above the surface — provides the vertical retreat option that matches the species’ documented tendency toward rotting wood retreats in the wild. A shallow water dish at substrate level provides hydration access. Our best tarantula cork bark guide covers appropriate pieces for Old World fossorial species with arboreal tendencies.
Substrate
Five to six inches of moisture-retaining substrate that holds burrow structure. Peat moss and coconut fibre give the moisture retention and structural firmness appropriate for the moist, organic-rich lowland rainforest floor of Sarawak. Adults need at least five inches of substrate and slings three inches minimum. The substrate should be maintained lightly to moderately damp throughout — this is a lowland rainforest species where consistent moisture in the substrate reflects the natural conditions far more accurately than the dry or moisture-gradient approach appropriate for savanna or desert species. Our best tarantula substrate guide covers moisture-retaining blends appropriate for Bornean lowland rainforest fossorial species.
Water And Humidity
A shallow water dish at all times, refreshed every two to three days. Humidity of 75 to 85 percent is appropriate for the consistently humid Bornean lowland rainforest habitat — meaningfully higher than semi-arid species and at the upper end of what most hobby enclosures routinely maintain. Good ventilation is essential alongside this humidity to prevent the stagnant air that causes respiratory stress — the same principle of moist moving air rather than moist stagnant air applies here as for all high-humidity species. A hygrometer confirms actual ambient conditions, and a fine-mist misting bottle handles targeted moisture additions without flooding the substrate.
Heating And Temperature
The Bornean lowland rainforest maintains consistently warm temperatures year-round with minimal seasonal variation. A captive range of 78 to 85°F suits this species, and most temperate indoor environments will need supplemental heat to maintain the warm end of this range consistently. A side-mounted heat mat controlled by a thermostat provides reliable background warmth. A thermometer at substrate level confirms actual enclosure conditions.
Diet And Nutrition
Crickets, dubia roaches, and other appropriately sized invertebrates every seven to ten days for adults. The fast growth rate documented for this species supports regular juvenile feeding to move through development efficiently. Food should be offered near the burrow entrance in the evening. Feeding tongs are essential — this is an Old World species with no urticating hairs and an extremely painful bite reported by keepers unlucky enough to have experienced it. Remove uneaten prey within 24 hours. Our best tarantula food guide covers feeder options and sizing for fast-growing Old World Bornean fossorial species.
Compatibility
Solitary only. Captive breeding of this species is still in its relatively early stages and any successful pairing contributes meaningfully to the hobby’s captive population of a species whose wild collection history makes responsible breeding particularly important.
Behavior And Temperament
Skittish and defensive describes the temperament accurately — an Old World species without urticating hairs whose defensive response skips the warning stages that New World species provide through hair-kicking. The species is known to be fast and the combination of defensiveness and speed means all enclosure work should be planned and carried out deliberately with long tools. The behavioural flexibility between deep burrowing, surface activity, and occasional arboreal behaviour means this species can be visible more frequently than strictly fossorial species — the neon blue legs appear at the burrow entrance during feeding and during periods of surface activity in a way that makes the visual reward genuinely accessible rather than dependent on luck. Our fossorial tarantulas article covers the deeper context of fossorial keeper expectations that applies to the burrowing aspects of this species’ behaviour.
Handling
Not recommended. The Old World temperament, defensive speed, and absence of urticating hairs make this a strictly hands-off observation and display species. The extraordinary colouration is best appreciated through the enclosure glass during feeding and surface activity periods, which given the species’ documented tendency to spend time above ground is not as rare an opportunity as with more strictly fossorial Old World species.
Health And Lifespan
Precise lifespan data is not yet well-established given the species was only described in 2019 — the captive history is too short to have produced long-term longevity records. Based on the Old World fossorial character and the compact adult size, females likely live 10 to 15 years. Primary health considerations are maintaining appropriate warm temperatures and the high humidity of the Bornean lowland rainforest habitat — allowing either to drop significantly will stress a species adapted to the consistently warm, moist conditions of one of the world’s most stable tropical climates. Our tarantula dehydration article covers identification and recovery for dehydration concerns in high-humidity Old World fossorial species.
Price
Among the most expensive tarantulas currently available in the hobby, reflecting the combination of extraordinary visual impact, rarity, controversial collection history, and limited captive breeding supply. Bug Cage Company and Spider Shoppe are among US vendors stocking this species when available. Slings typically sell for $60 to $150 USD with prices varying significantly by size and availability. Juveniles range from $120 to $250. Confirmed adult females command $300 to $600 or more depending on size and source — prices that reflect both the genuine rarity and the extraordinary demand this species generates. Source captive-bred specimens only, without exception — the controversy surrounding the species’ initial extraction from Borneo makes wild-sourced specimens both ethically unjustifiable and potentially legally problematic. Everything needed to provide appropriate Bornean lowland rainforest conditions for this remarkable spider is on our best tarantula products page.