The praying mantis, an iconic predator, undergoes a dramatic transformation from hatchling to adult. Like all arthropods, the mantis possesses a hard, external skeleton that provides structure and protection, but this rigid casing prevents continuous growth. To increase in size, the mantis must periodically shed its entire outer layer in a process known as molting (ecdysis). This biological event governs the mantis’s development and determines when it achieves its final, reproductive form.
Why Praying Mantises Must Molt
The primary reason a praying mantis must molt is the inflexibility of its outer body shell, the exoskeleton, which is composed mainly of chitin. This hardened cuticle acts like armor that cannot stretch or expand as the insect’s body mass increases. Growth is not continuous but happens in bursts immediately following the shedding of the old skin.
The molting process is triggered by hormones that signal the body to prepare a new, soft cuticle underneath the existing one. Once ready, the mantis stops eating and finds a secure place to hang, typically upside down. It forces hemolymph and air into its body, increasing internal pressure until the old exoskeleton splits along the back of the thorax. The mantis then slowly extracts itself from this old shell, which is a difficult and energy-intensive maneuver.
The Number of Molts from Nymph to Adult
A praying mantis progresses through several distinct developmental phases, with the period between each molt referred to as an instar. The number of instars before reaching adulthood varies, generally falling within a range of five to ten molts, depending on the species and sex. Smaller species may complete development in fewer molts compared to larger species, such as the Chinese mantis, which typically molts seven times.
The insect’s sex is a significant factor, as females often require one or two more molts than males. This difference relates to the female’s need for a substantially larger body size to accommodate egg production and the formation of the protective egg case (ootheca). Males mature faster and with fewer molts, allowing them to reach sexual maturity more quickly to search for mates.
The frequency of molting is also heavily influenced by environmental conditions, particularly temperature and food availability. Mantises kept warm and provided with constant prey grow faster, leading to shorter intervals between molts. In optimal conditions, a nymph may molt every two to three weeks, while limited food or cooler temperatures can extend the time between molts to five weeks or more. The final molt, known as the imaginal molt, transforms the wingless nymph into the sexually mature adult form, which often possesses fully developed wings.
Essential Conditions for a Successful Molt
Molting represents the most physically dangerous time in a praying mantis’s life cycle, requiring specific environmental conditions for survival. The most important requirement is adequate vertical space, as the mantis must hang unimpeded from a secure surface to allow gravity to pull it free from the old skin. The available hanging space below the mantis should be at least two to three times its body length to prevent the insect from becoming crippled or stuck.
Proper humidity is also a factor, as air moisture helps prevent the shed exoskeleton (exuvia) from sticking to the new, soft body underneath. If humidity is too low, the mantis may become trapped and unable to fully emerge, a condition known as dysecdysis or a mismolt, which is often fatal. The mantis is most vulnerable immediately after shedding while its new exoskeleton is soft and pliable, a stage known as the teneral period.
During the teneral period, which can last up to 24 hours for a nymph, the mantis remains inactive while its new skin hardens and its limbs straighten. The mantis must remain undisturbed during this process, as a fall or jostle can cause permanent deformities. It will not eat during the days leading up to the molt and should not be offered food again until the new exoskeleton is fully hardened.