Tarantula (Mexican Red Knee) — Newborn & Baby Care

Mexican Red Knee tarantula spiderlings emerge from the egg sac as tiny, pale creatures barely larger than a pinhead. In the first days after leaving the sac, they remain clustered together in a tight group, relying on the remnants of their yolk reserves for nourishment. During this period they are extremely fragile, and any disturbance to their environment can cause undue stress or even fatalities among the clutch.

The keeper's role during these initial days is largely one of observation and restraint. Resist the urge to separate the spiderlings immediately, as they benefit from the collective humidity and warmth of staying together briefly. The mother, if still present in a breeding scenario, may guard the sac or the newly emerged young, and it is best not to intervene unless the spiderlings are clearly at risk of being harmed.

Once the spiderlings begin to disperse on their own, typically within a few days to a week, they should be separated into individual containers. Mexican Red Knee spiderlings are not communal and will readily cannibalize siblings if left together too long. Prompt separation is one of the most important steps in ensuring the survival of each individual spiderling.

Temperature stability is critical during these first days. Spiderlings are far less tolerant of temperature swings than adults, and even brief exposure to cold or excessive heat can be lethal. Keep the ambient temperature in the range of 75 to 80 degrees Fahrenheit, and avoid placing enclosures near windows, vents, or other sources of drafts.

Individual spiderling enclosures do not need to be large. Small deli cups or pill vials with ventilation holes work well for the earliest instars. The enclosure should be just large enough for the spiderling to move freely, find its water source, and construct a small web mat. Overly large enclosures make it difficult for tiny spiderlings to locate prey and can lead to dehydration if humidity is not carefully managed.

Substrate should consist of slightly moistened coconut fiber or a similar material that holds moisture without becoming waterlogged. A depth of about one inch is sufficient for the smallest spiderlings. Avoid substrates that are dusty, overly dry, or prone to mold, as spiderlings are particularly vulnerable to respiratory issues caused by poor air quality within their enclosures.

Ventilation is a balancing act at this stage. You need enough airflow to prevent mold and stagnant conditions, but not so much that the enclosure dries out rapidly. A few small pinholes in the lid of a deli cup, combined with a lightly moistened substrate, typically strikes the right balance. Monitor the interior closely for condensation buildup, which can drown a spiderling if droplets form on the walls or lid.

Provide a tiny piece of cork bark or a small artificial hide for the spiderling to retreat beneath. Even at this early stage, Mexican Red Knee spiderlings exhibit the species' preference for a secure hiding spot, and having one available reduces stress and encourages normal behavior such as webbing and feeding.

Spiderlings do not need to eat for the first several days after emerging from the egg sac, as they are still absorbing nutrients from their yolk. Attempting to feed them too early is wasteful and can actually stress the young tarantulas, since uneaten prey items left in a tiny enclosure pose a threat to a vulnerable spiderling that has not yet begun to hunt.

Once the spiderlings have completed their first post-emergence molt, usually within the first week or two, they are ready to accept food. Appropriate prey items at this size include fruit fly larvae, pinhead crickets, or pre-killed and crushed small insects. The prey must be significantly smaller than the spiderling itself, as oversized prey can injure or intimidate a tiny tarantula into refusing food altogether.

Feeding should occur roughly once or twice per week, though individual appetite will vary. Some spiderlings are eager feeders from the start, while others may refuse food for extended periods, particularly around molting. Remove uneaten prey within 24 hours to prevent it from harassing or injuring the spiderling, and to keep the enclosure clean.

Pre-killing prey is a common and recommended strategy for the smallest spiderlings. A freshly crushed pinhead cricket placed near the spiderling's web mat allows it to scavenge without the risks associated with live prey. As the spiderling grows and gains confidence through successive molts, you can transition to live prey items of appropriate size.

Hydration is arguably the single most critical factor in spiderling survival. Mexican Red Knee spiderlings are small enough that dehydration can set in within hours in a dry environment, and it is the leading cause of death among captive-bred spiderlings of this species. Maintaining proper humidity levels from day one is essential.

Rather than relying on a water dish, which poses a drowning hazard for the tiniest spiderlings, keep one corner of the substrate lightly dampened. The spiderling will drink from the moist substrate and from any tiny water droplets that form on the enclosure walls after a light misting. As the spiderling grows through successive instars and becomes large enough to safely access a shallow dish, you can introduce a small bottle cap filled with fresh water.

Misting the interior of the enclosure lightly every two to three days is generally sufficient, but this depends heavily on the ambient humidity of your home, the ventilation of the enclosure, and the local climate. In arid environments or during winter when indoor heating dries the air, you may need to mist more frequently. In humid climates, less frequent misting prevents the dangerous buildup of mold.

Watch for signs of dehydration, which include a shriveled or deflated-looking abdomen and sluggish movement. A well-hydrated spiderling will have a plump, rounded abdomen relative to its body size. If you suspect dehydration, place the spiderling on a lightly dampened paper towel inside its enclosure for a few hours while increasing the overall moisture level of the substrate.

Molting is the process by which a tarantula sheds its old exoskeleton to grow, and it is a frequent occurrence during the spiderling stage. Mexican Red Knee spiderlings may molt every three to six weeks during the first year of life, depending on temperature, feeding frequency, and individual growth rate. Each successful molt brings a noticeable increase in size and often a subtle shift in coloration.

Before a molt, spiderlings typically stop eating and may become reclusive, spending most of their time hidden beneath their cork bark or within a web mat. The abdomen may appear darker than usual as the new exoskeleton forms beneath the old one. These pre-molt signs can last anywhere from a few days to a couple of weeks, and during this time the spiderling should not be disturbed or offered food.

The molt itself usually occurs while the spiderling is lying on its back, which can alarm new keepers who mistake it for a dying animal. Do not intervene during a molt under any circumstances. The process can take anywhere from a few minutes for the smallest instars to an hour or more as the spiderling grows larger. Even the slightest vibration or disturbance during a molt can cause a fatal interruption.

After a successful molt, the spiderling's new exoskeleton is soft and extremely vulnerable. Do not feed the tarantula for at least three to five days after molting, as the fangs need time to harden sufficiently to handle prey. The old exoskeleton, called the exuvium, can be left in the enclosure or carefully removed once the spiderling has moved away from it.

Spiderling health assessment relies heavily on observation, as there are no conventional veterinary diagnostics available for tarantulas at this size. The most reliable indicators of a healthy spiderling are regular feeding, consistent molting on a predictable schedule, a plump abdomen, and active movement within the enclosure during the evening and nighttime hours.

Mold is one of the most common threats to spiderling health in captivity. It thrives in the warm, humid conditions that spiderlings require and can rapidly overtake a small enclosure. If you notice mold growing on the substrate, on uneaten prey remains, or on the walls of the enclosure, rehouse the spiderling into a clean container with fresh substrate immediately. Prevention is the best approach: remove uneaten food promptly, avoid over-misting, and ensure adequate ventilation.

Mite infestations can also affect spiderlings, particularly if the substrate is sourced from outdoor environments or if prey items introduce them. Tiny white or brown dots moving independently on the substrate surface or on the spiderling itself are cause for concern. Rehousing into a sterile enclosure with fresh substrate is the recommended response, as chemical treatments are not safe for use on tarantulas.

A spiderling that refuses food for more than a month outside of a pre-molt period, shows a persistently shriveled abdomen despite adequate humidity, or exhibits unusual posturing such as curled legs while upright may be in distress. Unfortunately, treatment options for ailing spiderlings are extremely limited. The best course of action is to ensure optimal environmental conditions and minimize handling and disturbance.

Mexican Red Knee spiderlings should not be handled. At this stage of life they are far too small and fragile to withstand the mechanical stress of being picked up or manipulated by human fingers. Even a fall of a few inches onto a hard surface can rupture the abdomen of a tiny spiderling, resulting in a fatal injury.

When you need to move a spiderling, such as during rehousing or enclosure cleaning, use a soft paintbrush or a small piece of cardboard to gently coax it into a temporary container. Work slowly and calmly, as sudden movements can trigger a burst of speed from the spiderling that makes it difficult to track and easy to accidentally injure.

It is also worth noting that while adult Mexican Red Knees are known for their docile temperament, spiderlings of this species can be considerably more skittish and prone to flicking urticating hairs when startled. These tiny barbed hairs are an irritant to skin and eyes, and though they are less potent from a spiderling than from an adult, they can still cause discomfort. Always wash your hands after working with the enclosure.

Keep spiderling enclosures in a quiet, low-traffic area of your home, away from speakers, television sets, and other sources of vibration. Tarantulas perceive their environment primarily through vibration and touch, and constant disturbance from household noise can create chronic stress that suppresses feeding and growth.