Praying mantises (Order Mantodea) possess the ability to change their color, a trait that is often misunderstood. Unlike chameleons or octopuses, which shift their hue rapidly using specialized cells, the mantis undergoes a slow, morphological adaptation. This gradual transformation is not a rapid response to a threat but takes place over a longer period. The resulting coloration is fixed into the insect’s outer layer, allowing it to better match its environment for survival.
The Mechanism of Slow Color Adaptation
The color change in a praying mantis is directly linked to its growth process, specifically molting. The insect’s color is not regulated by quick-acting pigment cells, but by the physical incorporation of pigments into the new cuticle layer. This process is categorized as a morphological color change because it involves a structural alteration.
The new hue is fixed just before and during the formation of the new exoskeleton beneath the old one. Once the mantis sheds its old skin and the new cuticle hardens, the color is set until the next molting event. Pigments like carotenoids (yellow and green) and melanins (brown and black) are incorporated into the chitin matrix of the new exoskeleton.
Environmental Factors Determining Mantis Color
The trigger for a mantis to produce a specific color involves external environmental cues sensed before a molt. The most significant factor is the color of the background substrate where the mantis rests, such as green leaves or brown bark. Researchers have observed that nymphs reared in green containers develop a green phenotype, while those in brown containers become brown, demonstrating this environmental influence.
Other factors, like light intensity and humidity, also play a role in signaling the appropriate color. Low humidity and high light intensity, often associated with dry seasons or dying vegetation, tend to promote the production of brown pigments. Conversely, high humidity and lower light levels, typical of lush, growing seasons, encourage the development of green coloration.
The timing of the environmental sensing is crucial because the color is only fixed after the new exoskeleton hardens. While the change is typically between green and brown, some species can exhibit yellow or even pink variations to blend with specific flowers. A few species, like the Egyptian praying mantis, can even display fire melanism, turning black in response to environmental conditions that precede seasonal fires.
The Evolutionary Purpose of Mantis Coloration
The primary function of the mantis’s fixed coloration is crypsis, which is the ability to blend into the surrounding environment. This camouflage serves a dual purpose for these ambush predators. The coloration provides defensive crypsis, allowing the mantis to avoid detection by visual predators like birds and lizards.
Equally important is offensive crypsis, where the mantis’s blending allows it to remain motionless and undetected by its prey. By matching the color of a leaf or a stem, the mantis can wait patiently for an unsuspecting insect to wander within striking distance. This fixed, background-matching coloration is a highly effective survival strategy.
The evolutionary pressure is so strong that even within a single species, different color morphs exist to suit varying microhabitats. This specialized camouflage is a testament to their predatory lifestyle, where remaining hidden is the difference between catching a meal and becoming one.