Mexican Red-Knee Tarantula: Species Profile

Characteristics, Housing, Diet, and Other Information

Mexican redknee tarantula

Tom Applegate / Getty Images

The well-known Mexican red-knee tarantulas are actually two different species of spider that are native to the Pacific coast of Mexico. The Brachypelma hamorii and the Brachypelma smithi both have vibrant red "knees" that contrast with their dark body color, making them easy to distinguish from the other types of tarantulas. And while scientists say there are slight differentiating features between the two species—like subtle color and shape nuances—both are referred to as "red knees" in the pet industry and are coveted for their beauty, temperament, and long lifespan. The Mexican red-knee tarantula is a docile and slow-moving animal, and you can handle it regularly without causing it undue stress.

Species Overview

Common Name: Mexican red-knee tarantula

Scientific Names: Brachypelma hamorii or Brachypelma smithi

Adult Size: Leg span of about 5 inches

Life Expectancy: Females: 20 to 30 years; males: 10 years

Mexican Red-Knee Tarantula Behavior and Temperament

The Mexican red-knee tarantula is one of the most docile and calm tarantulas in the pet trade, making it ideal for beginner arachnid keepers. This spider rarely bites. However, like most tarantulas, it will eject urticating hairs from its abdomen and legs if it thinks it is in danger. These barbed and mildly toxic hairs act as a defense mechanism as they embed into a predator's skin or eyes, causing discomfort and irritation. In humans, the hairs can also cause an allergic skin reaction resulting in inflammation, rash, and itching. While this is nothing to worry about, the reaction can last for several hours or days.

Housing the Mexican Red-Knee Tarantula

A 20 gallon tank is a suitable home for the Mexican red knee tarantula. As a general rule, the width of the tank should be two to three times wider than the leg span of the spider, and only as tall as the spider's leg span if it were standing on end. The enclosure should be escape-proof, preferably with only a side opening; because tarantulas like to hang upside down at the top of the tank, this will prevent the spider from falling each time you need to service the tank.

The substrate or bedding should be a mix of peat moss, soil, and vermiculite and at least 4 inches thick and loosely packed, to allow for burrowing and to dampen any falls. Wood, cork bark, or half of a small clay flower pot can provide good shelter or a hiding spot for the tarantula. Adding a few fake plants also helps mimic its natural environment.

Maintaining a consistent temperature and humidity is an important element of Mexican red-knee tarantula care. The recommended terrarium temperature is around 75 to 80 degrees Fahrenheit, and can be achieved by using a heat mat under one portion of the tank. While supplemental heating is recommended for most North American terrarium environments, it's also important to give your spider a non-heated area to cool off should the tank get too hot.

Keep the humidity level at 60 to 70 percent, which can usually be achieved through evaporation from a water bowl. However, in some dryer homes, misting the tank may be necessary. If you see your spider hovering over its water bowl but not drinking, chances are your environment is too dry. Conversely, if it's continuously hiding out in a far corner of the terrarium, your enclosure is probably too humid. 

Food and Water

Adult Mexican red-knee tarantulas dine on live crickets and other large insects like locusts and cockroaches. This means that you must also raise and feed insects alongside your spider. Grasshoppers and other large bugs can be collected from your yard for feeding, however, their diet must not include pesticide-laden plants. A pinky mouse or a small lizard may be fed occasionally as a protein boost, but make sure to clean the remains from the tank immediately. Also, remove any uneaten live insects, as their constant movement may stress your pet spider once it's full. Mexican red-knee tarantulas usually eat once or twice a week and may take an annual break during a molt.

A small shallow water dish serves two purposes in the terrarium. First, it's a drinking source; second, the evaporation from the dish helps to maintain relative humidity in the tank. Make sure the dish is shallow and change it out daily to maintain a fresh and clean supply of water.

Common Health Problems

Most tarantulas are hardy creatures that rarely fall ill. However, due to their eggshell-like exoskeleton, even a fall from a short height can result in death. For this reason, you should always handle your spider while sitting down, preferably on a carpeted surface. Good husbandry practices should prevent this, but watch your spider closely to make sure it's not exhibiting signs of low humidity stress.

The mildly dehydrated tarantula may have a shrunken abdomen and can become inactive. A more severely dehydrated tarantula will have its legs curled underneath it to some degree. Once a tarantula becomes dehydrated, it requires tarantula first aid: Put the spider in a cup holding a wet paper towel. The lower abdomen of the spider is the location of the book lungs (tiny slits in the abdomen that serve as the air cavity), so it should never be placed in standing water, or it will drown.

As with all tarantulas, the red-knee tarantula will go through the process of an annual molt. During this phase, your spider may not eat for days or weeks, it may act lethargic and tired, and it may even roll onto its back with its legs in the air. Don't worry; it's not dead! Just leave your pet be and carefully monitor its transformation as it slowly emerges from its old, small exoskeleton. Once the molt is complete, remove the exoskeleton from the habitat and refrain from feeding your spider for three to five days. Also, you must avoid handling your spider during this time and for many weeks after. Your spider's new skin will be fragile and sensitive until it hardens, and any physical movement might tear it irreparably.

Purchasing Your Mexican Red-Knee Tarantula

Before you purchase a Mexican red-knee tarantula for a pet, be aware of its lifespan. A female pet tarantula is an extremely long-term commitment. Also take care to note that this spider, like most, is poisonous. While the mild venom of this species is rarely a threat to humans, it is possible to have an allergic reaction if you are bitten.

Since the Mexican red-knee is a popular breed, sourcing a spider from a pet store or breeder shouldn't be difficult. Purchasing from a reputable breeder, however, is highly recommended, mostly to assure the health of your pet. Breeders take great care of their spiders and practice proper husbandry and also human socialization techniques, assuring a well-adjusted pet.

Species Similar to the Mexican Red Knee Tarantula

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Article Sources
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  1. Brachyphelma smithi. University of Michigan Museum of Zoology.