It lives up to its name once again: in the bizarre “alien” mantis from the Peruvian rainforest, biologists have discovered an organ previously unknown in praying mantises. At night, the females turn out a Y-shaped structure on the back and move it like a tentacle. As the scientists explain, this organ is apparently particularly effective in exuding fragrances, so that Stenophylla lobivertex can also invite distant males to a rendezvous in the jungle.
The fascinating diversity of species and their often astonishing adaptations keep biologists and nature lovers enthusiastic. The biological richness of the South American rainforests offers many opportunities to be amazed. This is also home to numerous representatives of a particularly bizarre group of insects – the praying mantises (Mantidae). Worldwide there are more than 2500 species of these fishing horrors, some of which are amazing. Despite their prominence, many aspects of praying mantis biology are still unexplored and new species are constantly being discovered.
The alien mantis in sight
Stenophylla lobivertex did not enter the stage of insect research until 2000. Because of its particularly bizarre appearance, even for praying mantises, the species from the Amazon forests of Peru is also known as the alien or dragon mantis. With their bizarre body structures, the predatory insects, up to five centimeters in size, imitate dried-up leaves in which they lurk for prey. In this species, the biologist Frank Glaw from the Zoological State Collection in Munich came across the unexpected phenomenon, which he is now reporting on together with his colleague Christian Schwarz from the Ruhr University in Bochum.
The discovery came about during nocturnal field research work in the jungle of Peru: “In the light of my flashlight I saw maggot-like structures that peeked out from the back of an alien mantis and then quickly withdrew,” says Glaw. “When I did so, I immediately thought of parasites that eat the animal from the inside, because that happens not infrequently with these insects,” says the biologist. But when he and his colleague Schwarz took a closer look at the phenomenon in other specimens in Peru and in animals kept in captivity, it became clear: It is a previously unknown form of a pheromone gland in praying mantises.
A pumped up scent gland
The previously known versions are inconspicuous, but in the alien mantis the pheromone gland is pumped up by body fluid to form a Y-shaped structure and moves like a tentacle, the investigations showed. The fully everted organ is six millimeters long and one millimeter wide. Trachea can be seen through the thin membrane and the insect’s special blood gives the structure a greenish-blue sheen. The alien mantis females only use the conspicuous organ in the protection of darkness and when they are undisturbed, the observations showed. “If they are disturbed while wagging with the olfactory organs, they immediately pull the pheromone glands back,” the scientists write.
But why did the alien mantis develop this bizarre system? “We suspect that Stenophylla lobivertex can exude the pheromones with the evertable organ more efficiently and in a more targeted manner than other praying mantises,” says Schwarz. “This can be very important, especially with a species as rare as this – with a low population density – so that the sexes can be reliably found,” explains the entomologist. These beings have evidently developed a particularly effective “dating app” to meet in the jungle at night. Once again it shows that the rainforests of South America not only contain countless new species, but also completely unknown characteristics and behaviors are waiting to be discovered, say the scientists.
Source: Pensoft Publishers, technical article: Journal of Orthoptera Research, doi: 10.3897 / jor.30.55274