Molting and growth
Providing the correct humidity and temperatures is vital in the molting process. The mantis can get stuck in the molt if humidity is too low or too high.
Molting process
Every insect has a hard exoskeleton made of chitin that they have to shed to grow. Molting is the most dangerous point in a mantis life. Once the epidermis separates from the outer cuticle they swell and expand in their new cuticle. During this time their body is very soft and are entirely incapacitated. If knocked from their perch or if they don’t have enough space to expand it can cause deformities preventing them from walking or hunting.
When Mantis hang down from the previous skin to molt they can be nearly double in length. This is why the enclosures should be more vertical.
Keeping proper humidity levels, having adequate climbing space and removing uneaten prey items will help prevent most problems. Mantis like to hang from tops of their enclosure so having something like mesh or even a paper towel hot glued to the lid can provide for this.
Growth
Some insects go through complete metamorphosis which have a distinct egg, larval, pupa and adult stage. Others have incomplete metamorphosis where the nymphs look like miniature versions of the adult form.
Praying mantis undergo incomplete metamorphosis in which all stages of their life looks similar to their adult form except for wings. Nymphs hatch out as tiny versions of their adult counterparts only a fraction of the size. Each molt they can nearly double in size.
Both males and females will have wings as adults. Many species of females cant fly as they are too heavy.
It can take over 8 molts before the mantis reaches its adult stage. Females will often have more molts than males.
Regeneration
Like many invertebrates, mantis have the ability to regenerate a completely severed limb and heal damage from wounds after a molt. Adults cannot regrow any body part as they no longer molt. For a limb it will take generally two molts to fully regrow.