Praying mantises undergo a significant transformation during their development. They must molt, a process fundamental to their growth. Molting, scientifically termed ecdysis, is the cyclic shedding of their rigid outer layer, or exoskeleton. This process allows the insect to increase in size and is a defining characteristic of all arthropods.
The Biological Necessity of Shedding the Exoskeleton
The necessity for a praying mantis to molt stems from a physiological constraint. Like all insects, the mantis is encased in a rigid exoskeleton, or cuticle, primarily composed of chitin. While this protective armor provides structural support, it does not stretch to accommodate growth. To grow larger, the mantis must shed this restrictive outer layer, a process triggered by hormones. Before shedding, the insect forms a new, soft cuticle underneath the existing one, separating it from the old shell in a phase called apolysis. This internal preparation ensures the new, larger shell is ready, allowing growth to occur in sudden bursts.
The Physical Process of Ecdysis
Ecdysis is a physically demanding and vulnerable process requiring careful preparation. The mantis typically stops eating and becomes still, often hanging upside down from a secure surface, which allows gravity to assist in pulling the body free from the old skin. The molting sequence begins when the old cuticle splits, usually along the midline of the back, near the head and thorax. The mantis then slowly wriggles its body out, pulling its head, antennae, and legs free first; this stage is fraught with danger, as a fall or disturbance can cause a fatal “mismolt.” Emerging from the old skin can take 20 minutes to over an hour, after which the mantis hangs from the shed skin (exuvia) while the soft, new exoskeleton expands using hemolymph and air before the hardening process begins.
Timing and the Transition to Adulthood
Molting defines the juvenile life stage of the praying mantis, known as the nymph stage. Each period between molts is called an instar, and the mantis progresses through several of these. Molting frequency varies based on species, temperature, and food availability, but a mantis typically undergoes five to ten molts before reaching full maturity. Females often require one or two more molts than males to reach their larger adult size. The final molt marks the transition to the adult form (imago), resulting in the development of fully functional wings. Once the mantis emerges from its final skin, the new exoskeleton is soft and must harden—a process called sclerotization—which can take up to a day or longer, after which the mantis stops growing and will not shed its skin again.