Tarantulas begin their lives tiny, but their appearance changes dramatically as they grow. The term for a baby tarantula is a spiderling, often shortened to “sling” by enthusiasts. Although there are more than 1,000 known tarantula species worldwide, the early developmental stages share many common visual characteristics.
Appearance Immediately Following Hatching
The initial stage after hatching from the egg sac is called the post-embryo or pre-larva, and it looks very little like a spider. These newly hatched creatures resemble tiny, pale eggs with legs that are barely mobile, earning them the nickname “eggs with legs.” They are often translucent or pale white to yellowish, completely lacking the deep pigmentation of their parents.
At this nascent stage, the young tarantula’s abdomen appears disproportionately large and round compared to its tiny, underdeveloped legs. The post-embryo does not feed externally, instead relying on the remaining yolk sac for nutrition. This stage is usually spent entirely inside the protective silk egg sac, often undergoing its first molt while still encased within the sac.
Defining Physical Features of the Spiderling Stage
The spiderling, or “sling,” stage begins after the first few molts when the tarantula develops a more recognizable, albeit small, spider-like appearance. These young tarantulas are fully mobile and begin to disperse and hunt for themselves. Their size varies greatly by species, with terrestrial species often starting around 0.25 inches in leg span, while some arboreal species may be twice that size.
A distinctive feature of the sling stage is the presence of specialized hairs (setae) covering their bodies, although these are shorter and less dense than the mature adult coat. Many species display “juvenile colors,” which are muted shades of brown, tan, or gray, even if the adult will eventually be brightly colored. The body proportions remain somewhat “baby-like,” with a large, rounded abdomen that stretches easily to accommodate a meal, contrasted with a smaller carapace.
The spiderling’s exoskeleton, which is the hard outer layer, cannot stretch as the tarantula grows. To increase in size, the sling must periodically shed this outer layer through a process called ecdysis, or molting. Younger tarantulas molt with high frequency, sometimes as often as once a month, which allows for rapid growth and is the mechanism by which they change their appearance.
How Appearance Changes During Growth
The most significant change during growth is the acquisition of the final, species-specific adult coloration. Many tarantulas only develop their vibrant hues, such as deep blues, reds, or striking patterns, after several progressive molts.
The overall body proportions also shift dramatically as the tarantula matures. The legs lengthen significantly, and the carapace, or cephalothorax, becomes more prominent relative to the abdomen. This change results in a more streamlined and less disproportionate shape compared to the plump, rounded look of a young sling.
Reaching the adult appearance is defined by a series of growth stages, or instars, with the final characteristics locked in after the last maturation molt. While the adult coloration may begin to show in the juvenile phase, the full size and mature look are only achieved once the tarantula has finished growing, a process that can take years depending on the species.