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Western Black Widow
Latrodectus hesperus
The Latrodectus hesperus, the infamous 'Western Black Widow'. It is one of the most iconic and lethal true spiders (Araneomorphae) of the American continent. Females are the emblem of danger: bulbous and hairless body of a shiny raven black color, embellished by the infamous and fatal 'red hourglass' mark on the ventral abdomen. It is a weaver of chaotic three-dimensional webs (cobwebs) in which it perpetually stays upside down, ready to immobilize gigantic prey by throwing streams of sticky silk. Possesses a neurotoxic venom of severe medical relevance to humans (latrodectism). Strictly for super expert collectors, although the spider is timid and rarely prone to bite unless crushed.
- Taxonomy
- Class:ArachnidaOrder:AraneaeFamily:TheridiidaeGenus:LatrodectusSpecies:Latrodectus hesperus
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Environment
Terrestrial
Humidity
40 - 50 %
Day temperature
22 - 28 °C
Night temperature
18 - 21 °C
UVB
None
Species description
Taxonomy and range: UC Statewide IPM identifies Latrodectus hesperus as the western black widow and as the only black-widow species in the western United States. Its documented range extends from British Columbia and Alberta to Mexico, through the Rocky Mountains and into western portions of the Great Plains.
Documented appearance: UC Statewide IPM describes the adult female as about 13 mm in body length, shiny jet black, with a usually red marking on the underside of the abdomen. The hourglass pattern can vary from joined or separated triangles to minimal or, rarely, absent red coloration.
Natural context: The cited source records the species in hot, dry California desert conditions as well as mountain localities, and around holes, crevices, clutter, buildings and rock walls. These observations describe occurrence; they are not captive-environment parameters.
Care, breeding and tankmates
Safety boundary: UC Statewide IPM identifies the western black widow as posing the greatest potential envenomation threat to people in the western United States, while also reporting that bites are rare even where the species is common. This is a safety notice, not a handling or captive-care protocol.
Reproductive observation: The cited source describes yellowish, teardrop-shaped, tough egg sacs and reports about 300 eggs per sac. It does not establish a captive breeding method, environmental setpoint, compatibility rule or health protocol.
Geographic Origin and Distribution
This species originates from: Nord America (Deserti, boscaglie aride e aree urbane del Nord America occidentale).
Origin
Selective breeding and cultivarsExtra-Amazon South AmericaCentral America and CaribbeanNorth America
Terrestrial invertebrate profile
- Diet
- Carnivore
- Latrodectus hesperus requires a diet rich in live invertebrate prey, relying on its keen senses and agility to hunt. Common feeder choices include small crickets, fruit flies for spiderlings, and appropriately sized roaches. Their fast metabolism sometimes necessitates more frequent feeding schedules depending on their specific size and age. Hydration is also crucial, often obtained from the moisture in their prey or a fine mist. Uneaten prey should be promptly removed to prevent enclosure contamination.
- Adult size
- 1.3 cm
- The catalog's scalar value is 1.3 cm. The UC Statewide IPM — Widow Spiders source reports a maximum adult measurement of 1.3 cm for this species, recorded as body length. The taxonomic record consulted is Latrodectus hesperus. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Lifestyle/Microhabitat
- Terrestrial
- The lifestyle of Latrodectus hesperus demands a carefully structured environment that caters to its specific terrestrial or arboreal nature. Owners must ensure a proper temperature gradient, allowing the animal to thermoregulate as needed. Their enclosures should offer multiple hides and climbing opportunities if appropriate for the species. Solitary housing is absolutely necessary to prevent territorial disputes and injury. Maintaining high standards of hygiene is critical for their long-term health.
- Activity cycle
- Nocturnal
- The activity pattern of Latrodectus hesperus typically aligns with crepuscular or nocturnal cycles. During the day, they remain securely tucked away in their hides to avoid desiccation and predators. As light levels drop, they emerge to actively forage, hunt, or explore their immediate surroundings. Artificial lighting in their enclosure should mimic natural day-night cycles without being overly intense. Disruptions to this cycle can cause feeding strikes or lethargy over time.
- Sociality
- Solitary
- This highly venomous species is strictly solitary and aggressively cannibalistic, fiercely defending its irregular cobweb territory against any other spiders, including members of its own species. They must be housed strictly individually at all times to completely prevent inevitable, highly fatal encounters between heavily armed, violently territorial specimens.
- Reproduction
- Oviparous
- Reproduction in Latrodectus hesperus requires careful conditioning and precise environmental parameters to ensure success. The male must be properly introduced to the female's enclosure to avoid immediate predation or aggressive behaviors. Following successful mating, the female will typically begin to construct an egg sac after a gestation period that varies by species. It is crucial to monitor the temperature and humidity to ensure the viability of the eggs. Once the young emerge, they should be separated promptly to prevent cannibalism.
- Venom level
- Highly venomous
- They possess an exceptionally potent, highly medically significant neurotoxic venom that completely mandates immediate medical attention if an envenomation actually occurs. A serious bite can rapidly cause severe systemic symptoms, including extreme, agonizing muscle cramping, severe abdominal pain, profound sweating, nausea, and potentially life-threatening complications in highly vulnerable or sensitive individuals.
- Handling tolerance
- Display only
- Handling Latrodectus hesperus is generally strongly discouraged due to the risk of stress to the animal and potential injury. A fall from even a short height can result in a fatal abdominal rupture or severe trauma. If moving the specimen is absolutely necessary, use a soft catch cup or a sterile brush to gently guide them. Owners should respect the creature's need for personal space and observe them strictly as display animals. Avoiding direct handling minimizes the chance of unpredictable defensive bites or stings.
- Brumation
- Not required
- In its natural habitat, Latrodectus hesperus may experience seasonal cooling that slows down its metabolic rate. In captivity, true brumation is rarely required unless breeding is explicitly planned. If temperatures naturally drop during winter, feeding frequency should be adjusted accordingly to match their reduced metabolism. It is important never to let the enclosure become freezing or excessively damp during these cooler periods. Careful monitoring ensures the specimen remains healthy until warmer conditions resume.
- Molting
- Regular
- Molting is a critical and highly sensitive phase in the life cycle of Latrodectus hesperus. Leading up to a molt, they will often refuse food, become sluggish, and sometimes seal themselves entirely inside their hide. It is absolutely crucial to maintain proper humidity and never disturb the animal while it is molting. After shedding its exoskeleton, the animal will be extremely soft and vulnerable for several days. Feeding must be strictly withheld until the fangs or pincers have fully hardened to prevent fatal injuries.
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
