An international team of entomologists has described seven new species in the leaf insect genera Phyllium and Pulchriphyllium from Philippines, Vietnam, Indonesia and India.
Live adult female leaf insects showing intergeneric and intraspecific color variability: (A) Pulchriphyllium anangu photographed near Agumbe, India on May 17, 2022 by iNaturalist user vishwanathgowda; (B, C) Phyllium ortizi reared and photographed by Maxime Ortiz from France in captivity: (B) brown form female, (C) green form female. Image credit: Vishwanath Gowda / Maxime Ortiz / Cumming et al., doi: 10.3897/zookeys.1173.104413.
Stick and leaf insects (phasmids) are a group that has evolved remarkable morphological adaptations for botanical camouflage and mimicry.
Presently this group includes more than 3,000 known species distributed across most regions of the world, with dozens of species new to science described annually.
While most resemble sticks, bark, and twigs, rarer instances of mimicry such as mosses, lichen, and leaves do exist, allowing phasmids to blend seamlessly into their arboreal habitat.
Additionally helpful for their guise, these insects are typically nocturnal, with little to no movement during the day when visually oriented predators are most active, and even at night phasmid movements are often slow and deliberate, mimicking the swaying of leaves or branches.
One group of phasmids that mimic general leaf morphology of flowering plants particularly well are the Phylliidae, or true leaf insects.
These masters of leaf masquerade are widely distributed across the tropical regions of Asia, Australasia, and the Pacific.
Their flattened body form coupled with leaf-like venation patterns on the fore wings achieves the simulation of plant leaves in female phylliids.
The diversity in coloration and patterns representing different stages of leaf decay lends to the remarkable mimicry of leaf insects.
“Individuals of different leaf insect species are often counted as belonging to the same species based on their appearance,” said University of Göttingen’s Dr. Sarah Bank-Aubin.
“We were only able to identify some of the new species by their genetic characteristics.”
The seven new species of leaf insects are Phyllium iyadaon from Mindoro Island, Philippines; Phyllium samarense from Samar Island, Philippines; Phyllium ortizi from Mindanao Island, Philippines; Pulchriphyllium heracles from Vietnam; Pulchriphyllium delislei from South Kalimantan, Indonesia; Pulchriphyllium bhaskarai from Java, Indonesia; and Pulchriphyllium anangu from southwestern India.
“Some individual insects from India were previously thought to belong to a species that is widespread in Southeast Asia,” Dr. Bank-Aubin said.
“But now we found out that they are a completely new species of leaf insects.”
“The finding is important for species conservation: if all the individuals die out in India, it is not just a group within a species that is reduced, as was previously thought. In fact, a whole distinct species is being wiped out. This means that the Indian species is particularly important to protect.”
“There are around 3,500 known species of stick and leaf insects and there are currently just over 100 described species of leaf insect,” said Dr. Sven Bradler, also from the University of Göttingen.
“Although they only make up a small fraction of this diverse family of insects, their spectacular and unexpected appearance makes them unique.”
The discovery is described in a paper in the journal ZooKeys.
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R.T. Cumming et al. 2023. On seven undescribed leaf insect species revealed within the recent ‘Tree of Leaves’ (Phasmatodea, Phylliidae). ZooKeys 1173: 145-229; doi: 10.3897/zookeys.1173.104413
