Praying mantises use coloration to blend into their environment for hunting and survival. A mantis being brown has several scientific explanations, ranging from its genetic makeup to its immediate surroundings. This color variation, whether green, brown, or a mixture of both, allows these ambush predators to thrive in diverse habitats. Understanding why a mantis displays an earthy hue involves looking at its species, habitat factors, and its growth cycle.
Natural Coloration and Species Variation
The presence of a brown praying mantis often means it is genetically supposed to be brown. Many mantis species are naturally polymorphic, meaning individuals within the same species can be green, brown, or a mixed color morph due to inherited traits. For instance, species like the Chinese Mantis (Tenodera sinensis) or the European Mantis (Mantis religiosa) frequently occur in both brown and green forms.
The brown coloration offers superb camouflage in environments like dried grasses, tree bark, or leaf litter, which is where many mantises spend their lives. Some species, such as the Dead Leaf Mantis, have evolved to be exclusively brown, with body shapes that mimic dead plant matter. Therefore, a brown mantis may simply be exhibiting its natural, genetically determined color palette.
Environmental Factors and Chromatic Adaptation
For species capable of changing color, the brown hue is often the result of a process known as chromatic adaptation, triggered by external environmental cues. This adaptation is not instantaneous like a chameleon’s, but it is a strategic change that occurs over time. The mantis uses its environment to determine the most advantageous color for its next phase of life.
Factors such as the color of the substrate, the intensity of light, and the local humidity levels all influence the final color. If a developing mantis spends its time on brown bark or dry leaves, it is more likely to emerge brown after its next molt. This adaptive response maximizes crypsis, ensuring the mantis is visually concealed in its specific habitat.
The mechanism involves the movement of pigments within the mantis’s skin, which is influenced by these environmental factors. This color is then fixed in the new exoskeleton until the insect sheds its skin again. The adaptive color provides a substantial survival advantage, especially when the surrounding vegetation changes color with the season.
Color Change During the Molting Cycle
The molting cycle, the process by which a mantis sheds its old exoskeleton to grow, is the only time a mantis can change its primary color. This event is when environmental triggers translate into a physical color change. The decision to be brown or green is made in the hours or days leading up to the molt, based on the sensory input the mantis receives from its background.
A mantis nymph may go through seven or more molts before reaching adulthood, and the color may shift with each shedding. Nymphs are often more capable of dramatic color shifts between molts than adults, who typically retain their final color permanently. As the mantis prepares to molt, it may appear duller or temporarily take on a grayish-brown hue before the old skin is shed.
The new color is not fully realized immediately; it develops gradually over several days as the fresh, pale exoskeleton hardens. The timing of the molt is a window of opportunity for the mantis to reset its camouflage to match its current surroundings. Once the new cuticle is fully hardened, the color is set until the next growth stage, or permanently for adults.
When Brown Indicates Health Concerns
While brown coloration is most often a sign of healthy camouflage, an abnormal or patchy brown color can sometimes indicate a health issue, particularly for captive mantises. A sudden, dark, or sickly brown discoloration that appears outside of a molt is a cause for closer inspection.
Dark spots or general dark discoloration can be a symptom of a bacterial or fungal infection. Fungal issues, which thrive in warm, moist environments with poor ventilation, may appear as dark blotches that compromise the exoskeleton. A mantis that is abnormally dark brown or black and is also lethargic, refusing food, or showing signs of vomiting could be suffering from a serious internal issue.
Another situation is a failed molt, which can sometimes leave parts of the mantis with a crumpled, dark, or weak appearance. If the brown coloration is accompanied by an inability to move correctly, this suggests a complication during the shedding process. Dehydration can also cause a mantis’s overall color to appear dull and dark, though this is often accompanied by lethargy.