Metabolism and How It Works

 

Unlike many insects, the metabolism of a praying mantis is uniquely adapted to its lifestyle as an obligate carnivore. Every aspect of its biology is designed around capturing, digesting, and converting animal prey into the energy and nutrients needed for growth, hunting, moulting, and reproduction.

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For many years, it was assumed that mantises used energy in a similar way to spiders. Because they often spend long periods sitting motionless while waiting for prey, researchers believed mantises conserved large amounts of energy between meals and had an unusually low metabolic rate.

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However, studies have shown that this is not entirely the case. Although a mantis may appear inactive, its baseline metabolic rate is broadly similar to that of many other insects of comparable size. Even while resting, a mantis must continuously fuel essential cellular processes, tissue growth, digestion, respiration, and maintenance of its nervous system.

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What makes a mantis unusual is how dramatically its metabolism responds after feeding.

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The Cost of a Big Meal

 

Praying mantises are capable of consuming remarkably large meals. In some cases, a mantis can eat prey weighing more than its own body mass, with recorded meals reaching up to 138% of the mantis's body weight.

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Following a large meal, the mantis enters a period known as a specific dynamic action, where metabolism increases significantly to process the sudden influx of nutrients. Within 6 to 12 hours of feeding, the metabolic rate can double as the digestive system works to break down proteins, fats, and other nutrients.

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Because mantis meals are often exceptionally large and rich in protein, this elevated metabolic state can persist for several days. In some individuals, it may take up to four days for metabolism to return to normal resting levels after a substantial feed.

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This surge in nutrient availability is one reason why moulting frequently occurs after a mantis has eaten well. Large meals provide the raw materials required to construct a new exoskeleton beneath the old one and build additional muscle tissue before the next growth stage.

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Why Regular Feeding Matters

 

A mantis relies heavily on nutrients obtained from prey. Unlike herbivorous insects that can graze continuously, mantises must obtain the protein, amino acids, fats, vitamins, and minerals required for growth from comparatively infrequent but nutrient-dense meals.

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As a mantis prepares to moult, it begins producing a new exoskeleton underneath the existing one. This process requires substantial energy reserves and a steady supply of nutrients.

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If these metabolic demands are not met, the mantis may struggle to generate enough internal pressure and muscular force to successfully emerge from its old exoskeleton. The result can be a mismoult, deformities, weakness, or in severe cases, sudden death.

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Unfortunately, this is something most long-term keepers will encounter at some point. While husbandry factors such as humidity and ventilation play an important role, inadequate nutrition can also contribute significantly to moult-related complications.

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Breathing Without Lungs

 

Mantises do not possess lungs like mammals, nor do they have a closed circulatory system. Instead, oxygen is delivered directly to body tissues through a highly efficient network of microscopic tubes known as the tracheal system.

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Air enters the body through tiny openings called spiracles, located along the thorax and abdomen. Oxygen then travels through progressively smaller tracheae until it reaches individual muscles and organs.

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To keep this system functioning efficiently, mantises perform rhythmic abdominal movements. These gentle pulses are often visible when the insect is resting and become more pronounced after feeding, during activity, or at higher temperatures.

The contractions act like a biological bellows, drawing fresh air into the tracheal system and expelling carbon dioxide from the body.

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The Role of Haemolymph

 

The same abdominal movements also help circulate haemolymph, the insect equivalent of blood.

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Unlike mammalian blood, haemolymph does not transport oxygen. Instead, its primary role is to move nutrients, hormones, immune cells, and waste products throughout the body.

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Following a meal, haemolymph distributes the nutrients extracted from prey to developing tissues, muscles, internal organs, and the growing exoskeleton. During moulting, haemolymph pressure becomes especially important, helping the mantis split its old exoskeleton and expand into its new one before it hardens.

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Key Takeaway

 

A praying mantis may spend hours sitting perfectly still, but beneath the surface its metabolism is constantly working. Large, protein-rich meals drive powerful increases in metabolic activity, providing the energy and nutrients needed for growth and successful moulting. Combined with specialised breathing movements and an efficient tracheal respiratory system, this allows mantises to thrive as highly effective insect predators.

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💡 Keeper's Tip: A healthy, well-fed mantis is generally better equipped for moulting than an underfed one. While overfeeding should be avoided, maintaining a consistent feeding schedule with appropriately sized prey is one of the best ways to support healthy growth and reduce the risk of moult-related issues.