Sling means spiderling
In the hobby, sling is shorthand for a young tarantula. It does not refer to one exact size or instar.
They are more delicate
Small slings have less reserve, dry out more quickly and can escape through tiny gaps. Enclosure design therefore needs more attention to scale.
They may look nothing like adults
Juvenile colour can be plain or completely different from the famous adult pattern. Dramatic colour changes are normal in many species.
Feeding
Slings eat small prey and may accept pre-killed pieces. They generally feed more frequently than large adults because they are growing and moulting faster.
Enclosures
A compact, ventilated container with appropriate substrate and a small retreat is usually easier to manage than an oversized display enclosure.
Patience
Slow-growing genera can remain small for years. Buying a sling is often the cheapest way to obtain a species, but it also means accepting a long wait before adult size and sex are known.
Why sling care changes quickly
Sling husbandry is temporary by definition. A container that is perfect this month may be too small after two good moults, and a moisture routine that works in winter may dry too quickly in summer. Check the enclosure after each moult instead of assuming the original setup will remain suitable until the spider becomes a juvenile.
Small changes matter more at sling scale. A ventilation hole that would be irrelevant to an adult can be an escape route, a few millilitres of water can alter most of the substrate, and one oversized prey item can dominate the whole enclosure. Keeping the setup simple makes those variables easier to control.
The five-point sling check
For a quick routine check, ask five things: is the lid secure, is the spider able to retreat, is the moisture appropriate for the species, is drinking water available in a suitable form, and is there any live prey that should be removed? If those basics are right, the sling usually needs less interference rather than more.
Do not dig up a hidden sling merely to prove it is alive. Sealed burrows, webbed retreats and periods of food refusal are normal around moulting. Keep records and let the spider reappear on its own unless there is a concrete reason to suspect flooding, injury or another genuine enclosure problem.