Praying mantises are well known for being skilled, formidable, and successful hunters. Now a new species discovered in Peru has added another intriguing weapon to their arsenal – impaling their prey on specially adapted barbs on their legs. According to researchers, this is a novel hunting strategy not seen before in mantids, or in fact any insect, and they hadn’t even been looking for it.

Dr Julio Rivera, an entomologist at Universidad San Ignacio de Loyola in Lima, first came across a male specimen of the mantis in 2000 when a colleague captured it in the Tingo María tropical rainforest region of Peru, and brought it to the lab. In the following years, more specimens turned up and were added to the collection at the University, and not long after Rivera returned to Peru in 2017, a local student donated three living juveniles – enough for Rivera to attempt a proper taxonomic description.

Physical features suggested the mantis was likely a new species, so the goal of rearing juveniles was to get them to maturity to study their genitals. "[E]ach species has a distinct genital shape, which helps to define the species," Dr Rivera told IFLScience.

However, Rivera noticed when watching the youngsters hunt that they were doing something he'd never seen before. He observed one fail to catch a tiny fly, and instead got its spiny foreleg stuck on a plant stem. After untangling itself, it struck out again, spearing its prey on its forelegs.

"Upon closer observation of other hunting attempts, I realized the mantis was spearing its prey instead of grasping it as is known to be the rule for all praying mantises," Rivera said.

Like other mantises, its foreleg is covered in spines, but unlike others, C. simpiras' are forward-facing, trident-like tines covered in tiny barbs that grip and prevent its victim from escaping.

The “standard” fore tibia of P. kanjaris compared to the modified fore tibia of C. simpira. Yony Callohuari Yony Callohuari

"To be 100 percent sure, we filmed the mantis hunting and played it in slow motion, confirming its unusual hunting style," Rivera said. "This was a sort of “eureka!” moment for us."

Describing the species for the first time in the journal Neotropical Entomology, Rivera and co-author Yony Callohuari say Carrikerella simpira (in South American mythology, the simpira is a jaguar-like creature that uses its spring-like front leg to capture and strangle prey) appears to be the first insect known to impale prey with its legs.

A 3D-printed model of C. simpira's tibia to understand their unusual weapon. Yony Callohuari

"Other insects, such as assassin bugs, robber flies and lacewing larvae, do impale prey but using their specialized mouthparts. This is the first case of predatory insects impaling prey using their legs," Rivera told IFLScience. "The only other non-insect arthropod that has a similar strategy are certain species of mantis shrimp, whose frontal appendages look remarkably similar to the standard forelegs of praying mantises. These shrimps also spear prey (mostly fish) with lightning speed. Kind of an awesome coincidence."

Standard mantis hunting involves using their long legs armed with spurs, which they hook around their prey and sweep towards themselves to trap it. However, C. simpira is what Rivera calls a "microhabitat specialist." Due to its small size, it feeds on small invertebrates like mites that live in the lichen and moss it inhabits, but to feed on tiny food items is only efficient if you can catch plenty of food without expending too much energy.

"Evolving trident-like forelegs can be seen as an adaptation for taking advantage of this abundant resource in the most efficient possible way in these particular conditions," Rivera said. "In other words, this mantis evolved skillful ninja-like hunting techniques to specialize on the small and abundant prey items that exist in its preferred habitat."

Rivera describes the impaling technique as more refined than the usual praying mantis lunge, and incredibly precise. Some of the mites the mantises were observed spearing were just 0.5 millimeters long. To not miss, the mantis has to stab its prey at a particular angle. "Imagine trying to impale a pea with a toothpick: in order to succeed, the toothpick needs to be 90° relative to the pea’s grounds in order to pierce through it, otherwise you end up pushing the pea away," Rivera explained.

Like many mantids, C.simpira is also a master of camouflage. Some mantises mimic flowers, others mimic creatures like wasps. C. simpira mimics the gray-green lichen that grows on the tree trunks of its rainforest home to help it blend in and hide from its unwitting victims. It's a good job these jungle-dwelling beasties are under 4 centimeters (1.5 inches) big.