Ptiliidae is a family of very tiny beetles with a cosmopolitan distribution. This family contains the smallest of all beetles, with a length when fully grown of 0.3–4.0 millimetres (0.01–0.16 in). The weight is approximately 0.4 milligrams. They are colloquially called featherwing beetles, because the hindwings are narrow and feathery. The eggs are very large in comparison to the adult female (maybe half the length) so only one egg at a time can be developed and laid. Parthenogenesis is exhibited by several species.
The small size has forced many species to sacrifice some of their anatomy, like the heart, crop and gizzard. While the exoskeleton and respiration system of the insects seems to be the major limiting factors regarding how large they can get, the limit for how small they can become appears to be related to the space required for their nervous and reproductive systems.
There are around 600 described species in 80 genera, but large numbers of specimens in collections await description and the true number of species is likely to be much higher than this. Fossil ptiliids have been recorded from the Oligocene, roughly 30 million years ago from the Eocene, 46.2–43.5 million years ago, and from the Cretaceous Lebanese and Myanmar amber, dated to 125 and 95 million years ago, respectively. The family is divided into 3 subfamilies:
Temporal range: 125–Recent Ma
Actinopteryx is a genus of beetles belonging to the family Ptiliidae which is sometimes referred to as feather-winged beetles as the hindwings are narrow and feather-like.Baeocrara
Baeocrara is a genus of featherwing beetles named because of the intricate structure of their flight wings, which have a long fringe of hairs on their borders. They belong to the Ptiliidae family, and are minute: between 1 and 0.5 mm. They are mostly found in hollow fir stumps and other types of rotten wood, dung and plant detritus. They feed on fungal spores. They seem to be recent immigrants to Northern Europe possibly introduced by the import of sawmill products. They have been reported in the Czech Republic. They are one of the least known groups in the Coleoptera.Baranowskiella
Baranowskiella is a genus of beetles in the Ptiliidae family.Baranowskiella ehnstromi
Baranowskiella ehnstromi is the smallest known beetle in Europe. It lives only in the pores of the bracket fungus Phellinus conchatus, which grows on Salix caprea. Its length is ca. 0.45 millimetres (0.018 in) to 0.55 millimetres (0.022 in) and its width about 0.1 millimetres (0.0039 in).The beetle has been observed in Sweden, Finland, Austria and in the Czech Republic. It was first described, along with the whole genus Baranowskiella, in 1997 by Ptiliidae specialist Mikael Sörensson and named after entomologists Rickard Baranowski and Bengt Ehnström. The beetle has a simple sound producing organ. It can fly and its diet consists of fungi spores.Discheramocephalini
Discheramocephalini is a tribe of feather-winged beetles first proposed in 2009. It contains six extant genera, and one extinct genus.Discheramocephalus
Discheramocephalus is a genus of feather-winged beetles, the smallest beetles on earth, first found in Cameroon. It was originally described in 2007 as a monotypic genus (only a single known species). Six additional species were added in 2008, and two were added in 2013.Discheramocephalus brucei
Discheramocephalus brucei is a species of feather-winged beetle, the smallest beetles on earth, first found in Cameroon.Discheramocephalus elisabethae
Discheramocephalus elisabethae is a species of feather-winged beetle, the smallest beetles on earth, first found in Cameroon.Discheramocephalus jarmilae
Discheramocephalus jarmilae is a species of feather-winged beetle, the smallest beetles on earth, first found in Bolivia.Discheramocephalus mikaeli
Discheramocephalus mikaeli is a species of feather-winged beetle, the smallest beetles on earth, first found in Tanzania.Discheramocephalus minutissimus
Discheramocephalus minutissimus is a species of feather-winged beetle, the smallest beetles on earth, first found in Indonesia. This species' adults have a body length of approximately 400 to 426µm. According to Grebennikov, the main factor limiting miniaturisation of female insects is an egg size significant enough in size to produce viable larvae. This size threshold is sometimes overcome, reaching limits of 180 and 130 µm in females and males, respectively, according to the author. Brain size is possibly the second most important factor limiting miniaturisation in this class.Discheramocephalus semisulcatus
Discheramocephalus semisulcatus is a species of feather-winged beetle, the smallest beetles on earth.Discheramocephalus stewarti
Discheramocephalus stewarti is a species of feather-winged beetle, the smallest beetles on earth, first found in Bolivia.Nephanes titan
Nephanes titan is a beetle from the Ptiliidae family of dwarf beetles. N. titan is notable for its exceptionally small body and simple nervous system. With an average maximum body length of only a few hundred micrometers, the beetle is one of the smallest non-parasitic insects in the world.Despite its minuscule nervous system, the beetle is still capable of associative learning.Pteryx
Pteryx is a genus of beetles that is typically found in northern bogs in the Northern Hemisphere. They belonging to the family Ptiliidae which is referred to as feather-winged beetles as the hindwings are narrow and feather-like. Like most of the rest of the family, Pteryx are very small and live in rotting vegetative matter. They prefer rotting wood and are generally found under the bark of rotting logs or stumps.Ptiliinae
Ptiliinae is the largest subfamily of feather-winged beetles (family Ptilidae). About 80% of the described genera of these very tiny beetles are contained herein; however, many more genera and species await description.
Like all members of their family, they are usually found in rotting organic material in a wide range of habitats. The clutch genenerally contains only a single egg, which is very large in comparison to the adult female, sometimes half as long as the beetle itself.Scydosella
Scydosella is a genus of beetles that consists of only one species Scydosella musawasensis. The species is regarded as the smallest free-living insect, as well as the smallest beetle. They are among featherwing beetle, named because of their feather-like spiny wings. It was first discovered in Nicaragua, and described in 1999 by Wesley Eugene Hall of the University of Nebraska State Museum. The initial discovery consisted of very few specimens, and exact measurements were not conclusive. Because of their tiny size, they were difficult to observe under microscope after preservation. The generally accepted size was 0.300 mm in length. On 8 February 2015, Alexey Polilov of the Lomonosov Moscow State University collected 85 specimens in Chicaque National Park, Colombia. They were discovered on a layer of fungus on which they feed. From these specimens exact measurements could be made, and was found that the smallest individual is only 0.325 mm long. The largest individual is 0.352 mm long, and the average length of all the specimens is 0.338 mm. The body is elongated and oval in shape, yellowish-brown in colour, and its antennae are split into 10 segments.Staphylinoidea
Staphylinoidea is a superfamily of beetles. It is a very large and diverse group with worldwide distribution.Synchroidae
The Synchroidae are a small family of beetles with no vernacular common name, though recent authors have coined the name synchroa bark beetles. The family consists of three extant genera, Mallodrya, Synchroa, and Synchroina, with a total of nine species.
Extant Coleoptera families