Praying mantises are formidable predators, but they are not immune to parasites and pathogens. Identifying an infection requires close observation, as they often mask weakness until the condition is advanced. A healthy mantis is typically alert, actively hunting, and maintains a clean appearance. Recognizing subtle physical and behavioral changes is the first step toward determining if a mantis is hosting a foreign organism.
Behavioral Shifts Indicating Internal Issues
The presence of internal parasites, such as nematodes or bacteria, often first manifests through altered movement and general disposition. A mantis suffering from an internal issue may display noticeable lethargy, moving much slower than usual or showing a reluctance to move when disturbed. This decrease in activity reflects the parasite consuming the host’s nutrients, leading to a diminished energy state.
The mantis’s feeding habits are another telltale sign of internal distress. An infected individual might suddenly refuse to eat, display disinterest in live prey, or have difficulty consuming food. This is often accompanied by signs of digestive upset, such as diarrhea or the vomiting of brown liquid, indicating severe systemic compromise.
Grooming behavior can also shift dramatically when a mantis is ill. Healthy mantises spend considerable time cleaning their antennae, raptorial forelegs, and eyes to maintain sensory function. A sick mantis may cease grooming entirely, leading to a visibly dirty exoskeleton, or engage in frantic, unsuccessful attempts due to discomfort. Lack of proper grooming can also lead to the accumulation of fungal spores or mites.
Specific Signs of Horsehair Worm Infection
One of the most dramatic parasitic infections is caused by the horsehair worm, a type of Nematomorpha. This parasite manipulates the host’s nervous system to complete its life cycle. Infected mantises often become unnaturally active, especially around midday, and are compelled to seek out water sources.
This altered behavior results from the worm manipulating the mantis’s perception of light, attracting it to the horizontally polarized light reflected off water surfaces. The mantis is driven to enter the water, the necessary aquatic environment for the mature worm to emerge and reproduce.
The actual emergence of the worm is the conclusive sign of infection. The horsehair worm, which can be long, thin, and dark, sometimes measuring several times the length of the mantis, will exit the host’s body through the rear end. This event is typically fatal, as the parasite has spent weeks to months consuming internal tissues and causing immense organ damage.
Visible External Parasites and Fungal Growth
Identifying external issues requires a close visual inspection of the mantis’s exoskeleton, particularly around crevices and joints. Small, reddish or whitish specks clustered around the mouthparts, leg joints, or wing bases are often mites. While some mites are harmless, parasitic species cause significant irritation, leading to sluggishness and sometimes localized lesions.
Fungal infections, or mycosis, present as visible, mold-like growths on the body surface. Under humid conditions, these infections appear as fuzzy patches that are white, gray, or green, often starting on injured or persistently damp areas. Fungi like Beauveria grow into the exoskeleton, eventually killing the host and turning its body into a white, spore-producing mass.
Another external threat comes from certain flies, such as Tachinid flies, which lay their eggs on or near the mantis. The resulting larvae burrow into the host, feeding internally before emerging to pupate. Signs of this parasitoid activity include localized discoloration, a discharge from the abdomen, or a mantis that fails to reach its full size, resulting in stunted growth or a lack of fully developed wings.
What to Do If You Find an Infected Mantis
When an internal parasite, such as a horsehair worm, is suspected, successful intervention is rare. The damage caused by a mature internal parasite is usually irreversible, and attempts to force its exit, such as placing the mantis in water, are highly stressful and often accelerate the host’s demise. For a pet mantis, the best course of action is immediate isolation to prevent the spread of pathogens to other insects.
For minor external issues, such as a small number of mites, a gentle attempt at removal can be made using a moistened cotton swab to wipe the affected areas. If the mantis is heavily infested with mites, shows signs of spreading fungal growth, or is severely compromised, a consultation with an exotic animal veterinarian is advisable. For wild mantises, observation is the appropriate response, allowing natural processes to take their course.