Because of the composition of the exoskeleton. It must of necessity be tough to serve its function. Since it is inflexible, the organism has to periodically shed it (moult) in order to grow; a process called ecdysis.
Arthropods are more vulnerable when moulting because their new exoskeleton is soft and therefore more vulnerable to predators. The new exoskeleton takes a while to harden; many will hide and wait during this time.
Since an arthropod has an exoskeleton, it cannot grow bigger than the skeleton it is currently wearing. Therefore, they moult during which time they crack open their skeleton and step out of it. They then swell up to a bigger size and then harden another skeleton on their outside. But while they are moulting, they aer engangered because all of their soft body parts are exposed to the weather and to predators.
because the exoskeleton can not grow as the animal grows.
As the arthropod grows it needs more room in the exoskeleton and sheds the small shell in order to grow a larger size.
Right after moulting (ecdysis) an arthropod will be more vulnerable because its new "skin" or exoskeleton hasn't hardened up yet. Many of them will hide and wait for this reason.
Molting or moulting (ecdysis) allows arthropods to increase in size as they age. Since their exoskeletons are rigid they cannot grow until the old skin is removed.
The exoskelton of an arthropod is hard, and thus cannot accomodate growth. So an arthropod must periodically replace it.
The exoskeleton of arthropods is rigid, its inelasticity inhibits expansion. It has to be shed entirely for the organism to increase in size.
Arthropods molt (moult) in a process called ecdysis. It is necessary for growth because of the inflexibility of the exoskeleton. The old shell remnants are called exuviae. Note that the term 'anthropod' should not be confused with 'arthropod'; anthropods are humans or humanoids and do not moult in the canonic sense.
the outter skin. as the arthropod grows, the outter skin doesn't grow with it. than it gets rid of it by molting!
The main reason is how weak and vulnerable they are just after molting. The new exoskeleton is still soft to allow growth of the animal. The other is the reason they hide DURING molting - it renders them immobile, some species have to lie on their back for hours on end and can't defend themselves.
Most only do so in larval/juvenile stages, when it's time to grow. Some arthropods such as tarantula females continue growing and molting until death. Also, when damage has occurred (torn off leg for example) molting can be induced earlier to develop and grow new appendages. :)
An arthropod
The exoskelton of an arthropod is hard, and thus cannot accomodate growth. So an arthropod must periodically replace it.
Ecdysis is when an arthropod molts its exoskeleton. Molting is necessary. The arthropod exoskeleton is inflexible, so, for it to grow larger, arthropods must molt.
Arthropods molt (moult) in a process called ecdysis. It is necessary for growth because of the inflexibility of the exoskeleton. The old shell remnants are called exuviae. Note that the term 'anthropod' should not be confused with 'arthropod'; anthropods are humans or humanoids and do not moult in the canonic sense.
This is how they grow. The old exoskeleton splits, then the body expands rapidly before the new exoskeleton hardens.
exoskeleton, chitin, molting
the outter skin. as the arthropod grows, the outter skin doesn't grow with it. than it gets rid of it by molting!
Molting is beneficial because the arthropod has less protection from danger than it does with its new skeleton has hardened.
Molting
Molting
Molting
Its new exoskeleton is soft.
Moulting (ecdysis) is the most convenient strategy for an arthropod organism's growth owing to the rigidity of the exoskeleton. If it were less inelastic it could potentially be stretched or enlarged by other means. Moulting also seems to be exploited by many arthropod species for limb or process regrowth after amputation.