Tarantula (Cobalt Blue) — Newborn & Baby Care

Cobalt Blue Tarantula spiderlings emerge from the egg sac as tiny, pale creatures measuring only a few millimeters in leg span. During the first days of life, they remain clustered together near or within the remnants of the egg sac, drawing on the last of their yolk reserves. At this stage they are extremely fragile and should not be disturbed, handled, or separated from their siblings prematurely. The mother, if still present, may guard the sac and the newly emerged young, and removing her too soon can cause unnecessary stress to both parent and offspring.

In captive breeding situations, the keeper will typically separate the spiderlings from the mother once they begin to disperse on their own, which usually occurs within the first week or two after emergence. It is important to have individual housing prepared in advance, as Cobalt Blue spiderlings are cannibalistic and will consume siblings if left together too long. Small deli cups or vials with ventilation holes and a thin layer of moistened substrate work well as initial enclosures. Each container should be labeled and dated to track development from the very beginning.

The first few days are primarily about observation rather than intervention. Spiderlings at this stage are not yet feeding and are still absorbing internal nutrients. Resist the urge to offer food immediately, as uneaten prey items can stress or even injure a tiny spiderling. Instead, focus on maintaining proper humidity and temperature within the containers, and simply monitor for signs that the spiderlings are alert, responsive, and beginning to move independently.

Once Cobalt Blue Tarantula spiderlings have completed their first post-emergence molt and begin moving actively around their enclosures, they are ready for their first meal. This typically occurs within one to two weeks after leaving the egg sac. Appropriate first prey items include pre-killed or freshly crushed pinhead crickets, fruit fly larvae, or other very small invertebrates. The prey must be significantly smaller than the spiderling itself, as oversized food items can overwhelm and injure these tiny animals.

Feeding frequency at this stage should be approximately every four to five days, though individual spiderlings may vary in their appetite. Some will eagerly pounce on prey almost immediately, while others may take several days to show interest. Do not leave live prey in the enclosure for extended periods, as even a small cricket can cause damage to a molting or resting spiderling. If the spiderling does not accept food within a few hours, remove the prey and try again in a couple of days.

Hydration is equally important during this period. While spiderlings obtain much of their moisture from prey, the substrate should be kept lightly damp to maintain humidity levels between seventy and eighty percent. A tiny water droplet placed on the side of the enclosure or on a small piece of foil can provide an additional drinking source. Avoid standing water or overly saturated substrate, as spiderlings can drown in even the smallest puddles.

As the spiderling grows and molts through its earliest instars, prey size can be gradually increased. The goal is to offer food items that are roughly one-third to one-half the spiderling's body length. Consistent, appropriately sized feeding during these early weeks lays the foundation for healthy growth rates and successful molting throughout the juvenile stage.

Cobalt Blue Tarantula spiderlings progress through a series of molts known as instars, each representing a distinct stage of growth. The first molt after emerging from the egg sac transitions them from a soft, pale nymph into a miniature version of the adult, complete with functional fangs and the ability to hunt independently. Subsequent molts occur with increasing intervals as the spider grows, but during the spiderling phase, molts may happen as frequently as every three to six weeks under optimal conditions.

With each successive molt, the spiderling increases in size and begins to develop the characteristic blue coloration that gives this species its common name. Early instars are typically brown or gray, and the vivid blue sheen on the legs may not become apparent until the spiderling has completed several molts. This is perfectly normal and should not be a cause for concern. The rate at which coloration develops can vary between individuals, with some showing hints of blue earlier than others.

Tracking molt dates is an invaluable practice for any keeper raising spiderlings. Maintaining a simple log of when each molt occurs, the approximate size of the spiderling before and after, and any observations about feeding behavior or activity level helps establish a baseline for that individual's development. Deviations from an established pattern, such as unusually long intervals between molts or a sudden refusal to eat, can serve as early warning signs of environmental or health issues.

By the time a Cobalt Blue spiderling has completed its fourth or fifth molt, it will typically have reached a leg span of roughly one to two centimeters and will be displaying burrowing behavior consistent with the species' fossorial nature. At this point, the spiderling is transitioning toward the juvenile stage and will require adjustments to its enclosure and care routine.

Proper housing for Cobalt Blue Tarantula spiderlings prioritizes humidity, security, and appropriate scale. A container that is too large can make it difficult for a tiny spiderling to locate prey and can lead to stress from excessive open space. Small plastic deli cups, condiment containers, or purpose-built spiderling enclosures in the range of two to four ounces are ideal for the earliest instars. Ventilation is essential but should be limited to small pinholes to prevent excessive moisture loss while still allowing air exchange.

The substrate should consist of a moistened mix of coconut fiber, peat moss, or a similar material that holds humidity well without becoming waterlogged. A depth of one to two centimeters is sufficient for very young spiderlings, though even at this early stage, many Cobalt Blues will attempt to burrow. Providing a small starter burrow by pressing a pencil or similar tool into the substrate at an angle gives the spiderling a head start on establishing the underground retreat that is central to this species' behavior.

Temperature should be maintained between seventy-five and eighty-two degrees Fahrenheit, with humidity levels around seventy-five to eighty-five percent. These conditions mimic the warm, humid tropical forests of Southeast Asia where Cobalt Blues originate. Avoid placing enclosures in direct sunlight, near heating vents, or in areas with significant temperature fluctuations. A stable, warm room in the home typically provides adequate conditions, though supplemental heating with a low-wattage heat mat on a thermostat may be necessary in cooler climates.

Cleanliness is important even at this small scale. Remove uneaten prey items within a few hours of offering them, and spot-clean any visible waste or mold. Full substrate changes should be infrequent and performed only when necessary, as the disturbance of a complete teardown can be stressful for a burrowing spiderling.

Even as tiny spiderlings, Cobalt Blue Tarantulas display the reclusive, fossorial temperament that defines the species throughout its life. Within days of being housed individually, most spiderlings will begin excavating rudimentary burrows in the substrate. This burrowing instinct is deeply ingrained and should be encouraged rather than discouraged. A spiderling that has established a burrow will generally be less stressed, feed more readily, and molt more successfully than one that is exposed on the surface.

Cobalt Blue spiderlings are notably more skittish and defensive than many other commonly kept tarantula species at this age. When disturbed, they may bolt rapidly across the enclosure or retreat immediately into their burrow. This speed and defensiveness make handling inadvisable at any age, but especially so during the spiderling stage when their small size makes them easy to lose and difficult to recapture. All interactions should be conducted with long, soft-tipped tools such as paintbrushes or flexible forceps.

Feeding responses in young Cobalt Blues can be unpredictable. Some spiderlings are aggressive feeders that ambush prey within seconds, while others are more cautious and may wait until nighttime to hunt. Because this species is primarily nocturnal, offering food in the evening often yields better results. Observing feeding behavior over time helps keepers understand individual personality and adjust their care approach accordingly.

It is also common for spiderlings to web extensively around the entrance of their burrows, creating trip lines that alert them to passing prey. This webbing is a positive sign of a settled, healthy spiderling and should not be removed during routine maintenance.

Monitoring the health of Cobalt Blue Tarantula spiderlings requires attentive observation, as these tiny animals cannot be examined hands-on without significant risk of injury or escape. The most reliable indicators of health are consistent feeding, regular molting, and active burrowing behavior. A spiderling that feeds eagerly, molts on a predictable schedule, and maintains its burrow is almost certainly thriving.

Molting is the most vulnerable period in a spiderling's life. In the days leading up to a molt, the spiderling will typically refuse food, become lethargic, and may darken in color as the new exoskeleton forms beneath the old one. This pre-molt period can last anywhere from a few days to a couple of weeks. During this time, all prey items should be removed from the enclosure, and the substrate should be lightly misted to ensure adequate humidity. A failed or incomplete molt is one of the most common causes of spiderling mortality, and maintaining proper humidity is the single most effective preventive measure.

Signs that warrant concern include prolonged refusal to eat outside of a pre-molt period, a shrunken or shriveled abdomen indicating dehydration, lethargy without an approaching molt, visible mold or mites in the enclosure, and a spiderling that remains on the surface rather than retreating to its burrow. Any of these symptoms should prompt an immediate review of environmental conditions, particularly humidity and temperature levels.

If a spiderling appears stuck during a molt, do not attempt to manually assist unless several hours have passed and the situation is clearly dire. Gentle misting of the enclosure to raise humidity is the safest first intervention. In the event of a suspected health issue that does not resolve with environmental adjustments, consulting an experienced invertebrate keeper or an exotic veterinarian familiar with arachnids is advisable.

Raising Cobalt Blue Tarantula spiderlings inevitably involves some degree of uncertainty, particularly for first-time keepers. Not every spiderling will survive to adulthood even under ideal conditions, and understanding which situations are normal and which require intervention is a critical skill. A spiderling that refuses a single meal is not cause for alarm, but one that has not eaten in three weeks and is not in pre-molt may be experiencing a problem.

Dehydration is the most common killer of tarantula spiderlings in captivity. The signs are subtle at first, presenting as a slightly wrinkled or deflated abdomen, but can progress rapidly to lethargy and death if not addressed. If dehydration is suspected, gently misting the enclosure walls and ensuring the substrate is adequately moist will often correct the issue within a day or two. Providing a small droplet of water directly in front of the spiderling can also help, as some individuals will drink readily when water is placed within easy reach.

Molt complications represent the second most significant risk. A spiderling that has been in pre-molt for an unusually long time, or one that appears to have begun molting but has stopped moving partway through the process, may be in trouble. Maintaining high humidity during molt periods is essential, and keepers should resist the urge to intervene physically unless the spider has been visibly stuck for many hours. Even then, assistance should be limited to the gentlest possible measures, such as applying a tiny drop of water to the area where the old exoskeleton appears to be adhering.

Finally, sudden behavioral changes such as a previously active spiderling becoming completely unresponsive, curling its legs beneath its body, or displaying an unusual posture should be taken seriously. While some of these behaviors are normal pre-molt indicators, they can also signal more serious issues. When in doubt, consulting with experienced keepers through reputable invertebrate communities can provide guidance tailored to the specific situation.