Phylliidae

The family Phylliidae (often misspelled Phyllidae) is a family of stick insects and contains the extant true leaf insects or walking leaves, which include some of the most remarkably camouflaged leaf mimics (mimesis) in the entire animal kingdom. Because the family Phylliidae is the only one within the subfamily Phylliinae - which in turn is the only subfamily within the superfamily Phyllioidea - leaf insects are often equated with these taxa. They occur from South Asia through Southeast Asia to Australia.

The family Phylliidae (often misspelled Phyllidae) is a family of stick insects and contains the extant true leaf insects or walking leaves, which include some of the most remarkably camouflaged leaf mimics (mimesis) in the entire animal kingdom. Because the family Phylliidae is the only one within the subfamily Phylliinae - which in turn is the only subfamily within the superfamily Phyllioidea - leaf insects are often equated with these taxa. They occur from South Asia through Southeast Asia to Australia.

Characteristics

Leaf insects can reach body lengths ranging from (male of Microphyllium spinithorax) to (females of Pulchriphyllium giganteum and certain Cryptophyllium species). They are characterized by a body that is horizontally flattened and broadened to resemble a leaf (mimesis). Their legs are also optimally adapted to this leaf mimicry through leaf-like expansions (lobes). Depending on the species and origin, leaf insects appear in various shades of green, yellow, brown, or reddish; some are speckled, while others are nearly uniform in color. Certain species exhibit significant color variation. In some cases, species such as Pulchriphyllium crurifolium were described multiple times, resulting in a number of synonyms. Previously, it was assumed that individual species possessed highly variable body shapes and occupied vast geographical ranges. Recent studies indicate, however, that species formerly synonymized on this basis are almost all distinct, valid species with significantly smaller distribution ranges. Females are consistently larger and significantly broader than males, bearing a stronger resemblance to leaves. This is due to their very broad abdomen and short mesonotum. Furthermore, the forewings (tegmina) of adult females are typically developed as leaf-like covers that often conceal the entire abdomen. Hindwings (alae) are either absent or merely vestigial in most females; they are well-developed only in the majority of females of the genus Cryptophyllium, as well as in Phyllium ericoriai and Phyllium bonifacioi. The smaller, narrower males usually possess short forewings and fully developed — mostly typically transparent — hindwings that enable short flights. They also generally feature three simple eyes (ocelli) on the vertex between the compound eyes. Their antennae are distinctly longer than those of the females and bear bristles; they consist of 20 to 26 segments, whereas the females' antennae are always composed of nine segments and extend only as far as the length of the head. These antennae are often modified into stridulatory organs. The abdomen is formed from ten segments; the posterior nine are free, while the first is fused with the metanotum. A transverse groove on the underside marks the transition between the metanotum and the first abdominal segment. The subgenital plate is located at the end of the eighth abdominal segment, concealing the genital opening and the ovipore. Located on the tenth abdominal sternum of the males is the vomer, a movable sclerite that serves to anchor the male to the female's seventh abdominal sternum during mating. It is usually shaped in a species-specific manner and bears a hook in almost all species; only the males of Cryptophyllium species have vomers with two hooks.

Taxonomy

The subfamily Phylliinae comprises 120 valid species (as of July 2026), about half of which have been described since 2016. In addition to the fossil genus Eophyllium, thirteen extant genera are recognized, eight of which have been described since 2017.

Extinct species

A 47-million-year-old fossil leaf insect was discovered in the Messel Pit in 2005. Described in 2007 by Sonja Wedmann et al. as Eophyllium messelensis, it demonstrates that the distribution range of leaf insects was once significantly larger and not confined to Southeast Asia as it is today. The fossil is exceptionally well-preserved and bears a strong resemblance to fossilized leaves previously found at the Messel Pit. Its abdomen is laterally expanded, giving it a leaf-like appearance. The fossil resembles the males of extant leaf insects; while it shares similarities in size and other external characteristics, it also exhibits minor differences, such as in the reproductive organs.

Captivity

The first species began to be kept in the terrariums of European enthusiasts in the mid-1970s. While the Phasmid Study Group’s list originally included only eight species under ten entry numbers, many species, often originating from multiple collection sites, are now being bred. The popularity of specific species fluctuates depending on availability and husbandry requirements. The initial species kept belonged to the genera now known as Phyllium and Pulchriphyllium. Early Phyllium species in captivity included Phyllium siccifolium and Phyllium bilobatum or Phyllium cf. bilobatum the former was subsequently reclassified and described as Phyllium hausleithneri in 1999. Among the Pulchriphyllium species, Pulchriphyllium bioculatum and Pulchriphyllium pulchrifolium were initially common in captivity, though the two were sometimes confused, and the latter was at one point synonymized with the former. Subsequently, the parthenogenetically reproducing Pulchriphyllium giganteum entered captivity. The first species now assigned to the genus Cryptophyllium - Cryptophyllium westwoodii - also appeared early on, though initially under the name of the similar Cryptophyllium celebicum. Phyllium philippinicum became widely kept due to the ease of breeding it. From the turn of the millennium onwards, an increasing number of species entered captivity; today, approximately 14 Phyllium species, 6 Pulchriphyllium species, 12 Cryptophyllium species, and - representing its genus - Walaphyllium monteithi are kept and bred. With Comptaphyllium caudatum, a representative of the genus Comptaphyllium was also in culture, at least for a time. Breeding trials involving Nanophyllium asekiense are also expected to take place, following the successful hatching and rearing of this species from eggs at the Montreal Insectarium in 2018 and 2019. Nanophyllium australianum is also reportedly being bred in its native Australia.

References

External links

Phasmid Study Group: Phylliidae

Text derived from https://en.wikipedia.org/w/index.php?oldid=1374430173 under CC BY-SA 4.0; modifications have been made.