The praying mantis, recognized for its distinctive forelegs and predatory skill, often sparks curiosity. Placing this terrestrial creature in water reveals complex aspects of insect biology, anatomy, and parasitic manipulation. Submersion is not a straightforward case of drowning; instead, it exposes the unique mechanics of insect respiration and, surprisingly often, a bizarre biological interaction. The consequences of a mantis entering water vary significantly depending on whether the insect is healthy or secretly colonized by a parasite.
How Submersion Affects Insect Respiration
Insects do not possess lungs or utilize a circulatory system to transport oxygen, meaning they do not drown like mammals. Instead, they rely on a highly specialized respiratory system composed of a network of tubes called the tracheal system. Air enters this system through small, paired openings located along the thorax and abdomen known as spiracles.
The spiracles function as muscular valves that can be opened and closed to regulate gas exchange and minimize water loss. When a mantis is submerged, water covers and blocks these external openings, preventing air from entering the tracheal tubes. Death occurs not by water filling the lungs, but by asphyxiation, which is a lack of oxygen reaching the internal tissues.
This mechanism means the insect technically suffocates rather than drowns. Many species possess the ability to close their spiracles tightly, allowing them to survive brief periods underwater. However, prolonged submersion will eventually deplete the air reserves within the tracheal system. The mantis’s body will cease to function as tissues run out of oxygen.
The Role of the Horsehair Worm Parasite
Submerging a mantis frequently results in the dramatic emergence of a long, thread-like organism known as a horsehair worm (Nematomorpha). This occurs because the mantis is a host in the parasite’s life cycle, which requires water for the adult worm to reproduce. Mantises typically become infected by consuming an intermediate host, such as a cricket or grasshopper, that has previously ingested the worm’s microscopic larvae.
Once inside the mantis’s body cavity, the worm grows considerably, sometimes reaching lengths far exceeding the host. The parasite spends a substantial period feeding on the mantis’s internal fat reserves and tissues. When the worm reaches maturity, it must leave its terrestrial host and return to an aquatic environment to mate and lay eggs.
To achieve this return to water, the parasite engages in biological manipulation, effectively altering the mantis’s behavior. The worm releases biochemical signals that influence the host’s central nervous system, overriding its natural instincts to avoid water. Research suggests this manipulation may involve the worm producing proteins that mimic or interfere with the host’s own neurotransmitters, potentially by stealing and utilizing the host’s genetic code.
This manipulation drives the infected mantis to actively seek out and enter water, a behavior called hydrophilia. The mantis may be attracted to the light reflecting off water sources, mistaking the shimmer for a cue. When the mantis is submerged, the presence of water triggers the fully grown worm to exit the host’s abdomen. The mantis, often weakened and damaged by the parasite’s exit, typically dies shortly after the worm emerges.
Mantis Anatomy and Water Survival
When the mantis is uninfected, its physical structure provides natural protection against moisture and brief water exposure. The external shell, or cuticle, is composed of a naturally hydrophobic material that repels water. This water-repellent property is often enhanced by microscopic surface structures, such as fine hairs or wax layers, which prevent water from fully wetting the surface.
This hydrophobic exoskeleton helps keep the insect dry and prevents water from easily entering the spiracles during a rain shower or accidental splash. The insect’s physical structure and low density mean it may be briefly supported by surface tension when it falls into water, allowing it a short window to attempt to climb out. This buoyancy and water-shedding capacity aid immediate survival when encountering an unexpected water source.
If submersion is very brief, the mantis can often be recovered and survive, especially if it kept its spiracles closed. However, this natural defense is only effective against short-term exposure, not prolonged periods underwater, as respiratory needs will eventually necessitate gas exchange. The mantis does not possess specialized gills or mechanisms to extract dissolved oxygen from the water. Its survival mechanism relies on preventing water from entering its respiratory system, not adapting to the aquatic environment.