What a bolus is
A bolus is the compact indigestible material left after a tarantula has liquefied and consumed the usable parts of its prey. It can contain crushed exoskeleton and other remains.
What it looks like
Boluses are often small dark or pale pellets, sometimes wrapped in silk. Their appearance varies with prey type and can be mistaken for faeces or a dead feeder.
When to remove it
Remove accessible boluses during routine spot cleaning, especially if they stay damp or begin to mould.
Do not destroy the retreat
If a bolus is woven deep into a secure burrow or web retreat, leave it until it can be removed without tearing the enclosure apart unless it is causing a clear hygiene problem.
Tools
Use long forceps and know where the spider is before reaching into the enclosure.