Praying mantises are captivating insects that can host various parasites. Understanding these parasitic relationships offers insights into how different species interact within their environments.
Common Mantis Parasites
Praying mantises are most commonly affected by horsehair worms (Nematomorpha). These obligate parasites must live within a host to complete their life cycle. Their life cycle begins in aquatic environments where adults lay eggs.
Larvae hatch and are often ingested by aquatic insect larvae, which serve as intermediate hosts. When these insects mature and emerge, they may be consumed by a mantis. Inside the mantis, the horsehair worm grows, absorbing nutrients through its body wall.
Other parasites, such as certain parasitic wasps, also affect mantises. Some wasps, like Mantidophaga, lay eggs directly into the mantis’s ootheca (egg case), where larvae feed on developing mantis eggs. Another type, Podagrion, seeks out already laid oothecae to deposit its eggs. These wasps target mantis reproduction, while horsehair worms directly parasitize the living mantis.
Understanding Infection Rates
Infection rates vary considerably due to several factors. Geographic location plays a significant role, with horsehair worms more prevalent in tropical and subtropical regions. Environmental conditions, particularly the presence of water bodies, are crucial for the horsehair worm’s life cycle. Mantises living near ponds, streams, or other aquatic habitats are more likely to encounter infected prey.
The specific mantis species also influences infection susceptibility. Study methodology and the sampled population (wild versus captive) also affect reported percentages. While some online content has claimed infection rates as high as 95%, scientific observations suggest a range of 1% to 28% for wild mantises. Captive mantises fed lab-bred prey generally exhibit very low or no infection rates.
Effects on Mantis Behavior
Parasitic infection, particularly by horsehair worms, can alter a praying mantis’s behavior. As the horsehair worm matures inside its host, it manipulates the mantis’s nervous system. This causes the mantis to seek out water bodies, a behavior uncharacteristic for these terrestrial insects. The worm achieves this by secreting proteins or chemicals that influence the mantis’s brain, compelling it towards water.
Research indicates infected mantises may be attracted to horizontally polarized light, reflected off water surfaces, guiding them to water. Once the mantis enters the water, the mature horsehair worm emerges to complete its reproductive cycle. The mantis typically dies shortly after the worm exits, as the parasite has consumed much of its internal tissues and organs.
Are Mantis Parasites a Threat to Humans?
The parasites commonly found in praying mantises, especially horsehair worms, do not pose a threat to humans or pets. These parasites are highly host-specific, completing their life cycle only within certain insect hosts. They cannot infect mammals, birds, or fish. Therefore, encountering a mantis with a parasite carries no risk of infection for people or household animals.