In general a bird spider becomes rather big, some of them even very big, up to a span of +/- 30 cm!
To be able to grow, a bird spider needs to shed old skin. Every time a bird spider changes its skin
it gets a beautiful colour and it grows a lot. This moulting is quite a process.
Before it starts moulting the spider will stop eating for a while, then you will suddenly find it flat on its back with its legs up in the air stretched out on a thin–woven mat. This all looks rather strange but is very normal for this process.
Once on its back its blood pressure starts to rise and the spider will burst open, first on the front side (cephalothorax) followed by the abdomen and the flank. Afterwards it will lie sideways and you can see the legs slowly slide out of the old skin, this is truly a wonderful sight.
After moulting the spider will stretch out and lie peacefully, a beautiful colour on its legs. This is to let everything become hard such as the teeth that now look soft and white. Only once the teeth are hard and have a dark colour can you start feeding the spider which is famished by the exhausting moult.