Praying mantises are captivating insects known for their distinctive appearance and predatory habits. These creatures, with their often green or brown camouflage and unique forelegs held as if in prayer, inhabit various environments globally. One intriguing characteristic is their ability to continue functioning for a period even after losing their head.
The Remarkable Survival of a Headless Mantis
A praying mantis can survive for several days, or even up to a week, without its head. While it may seem counterintuitive, the mantis’s physiology allows for this temporary continuation of basic bodily functions. The headless body can still move, respond to stimuli, and maintain some reflexes.
Biological Factors Enabling Decapitation Survival
The ability of a praying mantis to survive decapitation stems from its unique biological makeup. Unlike vertebrates, mantises possess a decentralized nervous system. Instead of a single, highly centralized brain, they have clusters of nerve cells called ganglia distributed throughout their body segments. The ganglia in the thorax control limb movements and other motor functions, allowing the mantis to walk or react without its head.
Respiration in a mantis also contributes to its headless survival. Mantises do not breathe through their heads or lungs. Instead, they respire through small openings called spiracles, located along their thorax and abdomen. These spiracles connect to an internal system of tubes called tracheae, which directly deliver oxygen to cells throughout their body. This decentralized breathing system means that head loss does not immediately stop oxygen supply.
A mantis also has an open circulatory system. Hemolymph, the insect equivalent of blood, flows freely within the body cavity, directly bathing organs and tissues. This system operates under low pressure and does not rely on a single, centralized pump or a complex network of vessels that would be compromised by decapitation. The circulation of hemolymph, which transports nutrients and waste but not oxygen, can continue independently of the head.
The Inevitable End for a Headless Mantis
Despite its remarkable ability to survive for a period without a head, the mantis’s eventual demise is certain. The head performs actions indispensable for long-term survival, primarily feeding and drinking. Without its mouthparts and sensory organs, a headless mantis cannot consume food or water.
This inability leads to an inevitable decline through starvation and dehydration. The lack of nourishment weakens the insect until its bodily functions cease. Additionally, the open wound left by decapitation makes the mantis highly susceptible to infection from bacteria or fungi. Such infections can further accelerate its decline, as the body’s defenses are compromised.
Sexual Cannibalism and Head Loss
The scenario of a praying mantis losing its head is most frequently associated with sexual cannibalism, a behavior observed in various species during mating. The female mantis sometimes consumes the male, often starting with his head, either during or shortly after copulation. This behavior is not universal across all mantis species, but it is well-documented in many.
This act can benefit the female by providing her with a significant source of protein and nutrients. This additional nourishment can contribute to the production of more eggs, thereby increasing the male’s reproductive success, albeit posthumously. The male’s copulatory movements are controlled by nerve centers in his abdomen, not his head, meaning that decapitation does not necessarily interrupt the mating process and can even sometimes enhance it by removing inhibitory signals from the male’s brain.