Brachypelma smithi, commonly known as the Mexican red-knee tarantula, is one of the most popular species of tarantula in the pet trade. With its striking appearance and docile nature, it has captured the interest of both beginner and experienced tarantula keepers. One of the most common questions people ask when considering owning a Brachypelma smithi is: How big do these spiders actually get?
In this article, we’ll take a detailed look at how large Brachypelma smithi can grow, their growth process, factors that influence their size, and other relevant details that are important for understanding and caring for this species.
Understanding the Basics of Brachypelma smithi
Before diving into size specifics, it’s important to first understand what Brachypelma smithi is. This tarantula species is native to Mexico and is easily recognized by its beautiful red-orange markings on the knees of its legs, contrasting against a dark, brownish body. While this species is not the largest tarantula, it is certainly one of the most admired due to its beautiful coloring and relatively calm temperament.
Lifespan of Brachypelma smithi
The lifespan of Brachypelma smithi is another important factor to consider when thinking about how big they will get. Female tarantulas, in particular, have a much longer lifespan than males.
Females: Can live for 20 to 30 years, sometimes even longer under optimal conditions.
Males: Generally live much shorter lives, with a typical lifespan of 5 to 8 years.
Males mature much faster than females, so they may reach their adult size and then pass away in a few years after mating.
Average Size of Brachypelma smithi
Brachypelma smithi is considered a medium-sized tarantula compared to other species, but it’s still relatively large in the tarantula world. The size of a Mexican red-knee tarantula is usually measured by its leg span—the length of the spider’s legs when fully extended—and not by its body length. The leg span of a fully grown Brachypelma smithi can range between 5 to 6 inches (12.7 to 15.24 cm), with some individuals occasionally reaching slightly larger sizes.
Male vs. Female Size Differences
As with many other tarantula species, there is a noticeable difference in size between males and females of Brachypelma smithi.
Female Brachypelma smithi: Females are significantly larger than males. They typically reach their full size at around 4 to 5 years of age. When fully grown, females can have a leg span of 5 to 6 inches (12.7 to 15.24 cm), with some individuals growing even larger.
Male Brachypelma smithi: Males mature much faster than females, typically reaching full size within 1 to 2 years. However, they are smaller overall, with an average leg span of 4.5 to 5 inches (11.4 to 12.7 cm). Males are typically more slender and smaller in body size compared to females.
So, while female Mexican red-knee tarantulas tend to be more robust and larger, males are still quite impressive but never as large as their female counterparts.
Growth Process of Brachypelma smithi
The size of a Brachypelma smithi increases over time through a process known as molting. Like all spiders, Brachypelma smithi undergoes a series of molts as it grows. These molts are necessary because the tarantula’s exoskeleton does not expand as it grows. Instead, the spider must shed its old exoskeleton to reveal a new, larger one.
How Molting Affects Size
Molting occurs at regular intervals, especially when the spider is younger and still growing. After each molt, the Brachypelma smithi will usually grow in size, including the legs and body, until it reaches its full adult size.
Juveniles: A young tarantula, or juvenile, can molt every 3 to 6 months during its active growth phase.
Adults: Once the tarantula reaches maturity, the frequency of molts decreases. For adult female Brachypelma smithi, they may only molt once every 1 to 2 years.
Because of this molting process, the growth of the tarantula can seem slow, but over time, the size increase is very noticeable.
Growth Timeline
Brachypelma smithi grows gradually over its lifetime, with some interesting milestones along the way:
Egg sac: After mating, female Brachypelma smithi lays eggs in a silk egg sac. These egg sacs can contain anywhere from 100 to 500 eggs. After hatching, the spiderlings are tiny, measuring just 1/4 inch (0.64 cm) in length.
Spiderlings: When they hatch, spiderlings are incredibly small and take several months to develop into juveniles. During the early stages of growth, they molt several times before they are big enough to be considered juvenile tarantulas.
Juvenile stage: From 1 to 3 years old, Brachypelma smithi spiders are considered juveniles. During this period, they will experience frequent molts and grow significantly in size.
Adulthood: By the time they are 4 to 5 years old, female Brachypelma smithi have reached their full size, while males generally reach maturity around 2 years of age. At this point, they will molt much less frequently, and their growth will slow down.
The process from hatchling to adult can take anywhere from 3 to 5 years, depending on the sex and environmental conditions.
Factors That Affect Size
While the average size of Brachypelma smithi is around 5 to 6 inches in leg span for females, several factors can influence their final size.
1. Diet
A well-balanced diet is crucial for the healthy growth of any tarantula. Brachypelma smithi is a carnivorous species and should be fed a variety of prey, such as crickets, roaches, and other insects. Providing regular meals ensures the spider gets the nutrients it needs for growth and development. Malnutrition or irregular feeding can result in stunted growth or poor molting.
2. Temperature and Humidity
Brachypelma smithi thrives in warm, dry environments. Keeping them in an environment that mimics their natural habitat in Mexico is essential for proper growth. The ideal temperature for this species is 75°F to 85°F (24°C to 29°C), with humidity levels around 60% to 70%. Too much humidity or a drastic change in temperature can cause stress, affect molting, and hinder proper growth.
3. Enclosure Size
Though tarantulas do not grow directly based on the size of their enclosure, providing an adequate space for them to roam and exercise can help them grow healthy. Overcrowded or undersized enclosures may cause stress, leading to slower growth or health issues.
4. Genetics
Like all animals, genetics play a significant role in determining the final size of an individual Brachypelma smithi. While environmental factors are essential, a tarantula’s genetics will ultimately determine if it reaches the higher end of the size spectrum or stays on the smaller side.
Brachypelma smithi Behavior and Size
Even though Brachypelma smithi are not the largest tarantulas, their size is imposing enough to make them fascinating creatures to observe. When fully grown, their long, thick legs and large body make them one of the most beautiful and dramatic tarantulas to keep as a pet.
Despite their size, Brachypelma smithi is well-known for its calm demeanor. They are often considered to be docile and are less likely to show aggression compared to other tarantula species. Because of this, they are great choices for beginners and those who want to handle their tarantula with care.
Conclusion
Brachypelma smithi, or the Mexican red-knee tarantula, can grow to a respectable size, with females reaching up to 5 to 6 inches in leg span and males being slightly smaller. The growth of a Brachypelma smithi is a gradual process, influenced by factors such as diet, temperature, humidity, and genetics. With proper care, these beautiful tarantulas can thrive and grow into impressive specimens.
Whether you’re thinking of getting a Brachypelma smithi as a pet or simply curious about their size, knowing how big they can get is an important part of understanding this fascinating species. With the right conditions, these spiders can reach their full size and live for many years, making them a rewarding pet for spider enthusiasts.
Related topics: