Praying mantises, like all insects, possess an external skeleton that provides structure and defense, but this rigid armor cannot stretch to accommodate a growing body. The process of shedding this outer layer is known as molting, a necessary biological event that allows the mantis to increase significantly in size. Molting is a period of intense physiological change, governed by hormones, that temporarily replaces the mantis’s hard protection with a soft, expansive new exterior.
Why Praying Mantises Must Molt to Grow
The biological drive behind molting is the unyielding nature of the exoskeleton, a hard outer layer primarily composed of chitin. This armor prevents continuous growth, requiring the mantis to periodically construct a larger one beneath the surface and discard the old structure.
Growth occurs in distinct, rapid spurts immediately after the old skin is cast off. Mantises are hemimetabolous insects, progressing through three life stages: egg, nymph, and adult. Nymphs undergo this shedding process, typically molting between five to ten times before reaching maturity.
Each stage between molts is called an instar. Once the mantis completes its final molt, reaching the sexually mature adult stage, the need to shed skin ceases entirely. The adult form is fixed in size and no longer needs to replace its hardened exterior.
The Mechanics of Shedding: Ecdysis
The shedding of the cuticle is formally called ecdysis, a complex and physically demanding process. Before it begins, the mantis stops feeding and becomes inactive for several days while secreting a fluid that separates the old exoskeleton from the newly forming, soft cuticle underneath.
The mantis must find a secure anchor point, usually hanging upside down, allowing gravity to assist the extraction. To physically split the old skin, the mantis utilizes internal hydrostatic pressure by pumping air and hemolymph (the insect equivalent of blood) into its body. This internal inflation causes the old cuticle to crack along a pre-determined seam, typically down the back of the thorax.
Once the split occurs, the mantis slowly extracts itself, maneuvering its head, legs, and raptorial forearms out of the old shell. This extraction can take a half hour to several hours, using a slow, wriggling motion. The discarded skin is known as the exuvia.
The Vulnerable Period and Final Transformation
Emerging from the old skin leaves the mantis in a delicate and vulnerable state. The new exoskeleton is soft, pale, and pliable, offering almost no protection. During this brief period, the mantis undergoes a rapid expansion, inflating its body and limbs with hemolymph to achieve a larger size before the new cuticle hardens.
The mantis must remain suspended and motionless, allowing gravity to help straighten and shape its new, soft limbs and body. Over the next several hours, the new exterior begins sclerotization, which involves the cross-linking of proteins to make the cuticle rigid and dark, restoring the mantis’s defense. Full hardening can range from 24 hours for a small nymph to several days for a sub-adult.
The final molt is the most significant, marking the transition to the winged adult form. During this ultimate ecdysis, the small wing pads present on the nymph inflate and expand into fully developed, functional wings. Once the final exoskeleton is fully hardened, the mantis is reproductively mature.