The Phylliidae: true leaf insects

Phyllium philippinicum
Credit: Insectarium de Montréal (René Limoges)
Phyllium philippinicum
  • Phyllium philippinicum
  • Phyllium giganteum (Cameron-highlands, Pahang, Malaysia - 1992)
  • Phyllium jacobsoni (Mt. Argopuro, East Java, Indonesia - 2017)
  • Phyllium bioculatum (Mt. Salak, West Java, Indonesia - 2006)
  • Phyllium brossardi (Ranau, Sabah, Malaysia - 2007)
  • Phyllium Bioculatum - Egg
The Phylliidae: true leaf insects

Written on January 23, 2018

Among insects that bear a strong resemblance to leaves, the Phylliidae are probably the most remarkable. The first naturalists to observe them named them walking leaves!

A small family

No more than 70 species of Phylliidae exist. This family of rather rare insects is among the most spectacular and the most fascinating on the planet. They’re found in the tropical environments of Asia – the area from India to Australia – with a few species on the Fiji Islands.

Fascinating insects

Among Phylliidae there’s a highly marked sexual dimorphism. The males, slender of build, possess long, fine antennae. They fly well and are drawn to light, which is why greater numbers of them can be found in in collections.

In contrast, the females aren’t capable of flight. Bigger and more flattened, their bodies strongly resemble leaves, with short antennae and foliate legs.

A biology still hardly known

Specialists think that a number of Phylliidae species live way up in the tropical rainforest canopy, between 20 and 60 meters high. They live on their host plant and feed on other plant material. During her lifetime, each female will lay about 100 eggs at the top of the tree.

Those eggs, small and looking like seeds, have little fins that allow them to be dispersed by the wind. The shape of the eggs varies from one species to the other, and the eggs are important in terms of species classification. When they hatch, the larvae are often of a red or black color. They’ll gradually change their coloring in the course of successive molts, eventually all turning green. The life cycle is quite long, but adults live no more than a few months.

Phylliidae have very little in the way of defense, apart from blending in almost perfectly with the leaves of their habitat. Certain Phylliidae take that mimicry to an extreme: the tips of their green wings are smudged with shades of brown reminiscent of dead leaves. In nature, Phylliidae go so far as to imitate the movement of leaves in the wind by rocking back and forth when they walk.

The study of Phylliidae and the description of new species

Recently, important studies have been undertaken on Phylliidae, including DNA tests on numerous specimens, the aim being not just a better understanding of their diversity but also to try to group together males and females that had been described under various names although belonging to the same species. The family today consists of four genera, these being Chitoniscus, Microphyllium, Pseudomicrophyllium and Phyllium.

It was in working with these researchers and in examining extensive series of Phylliidae that it was possible to discover and describe two new Phylliidae species of the Phyllium genus. These new species, Phyllium bourquei and Phyllium brossardi (described by Cumming & Le Tirant), were named in honor of Pierre Bourque and Georges Brossard, two founders of our institution.

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