Common name: Featherwing beetles
Number of species: 75
Size Range: 1-1mm
Description:
Ptiliidae contains 75 of the smallest insects in Britain, all 1mm or less in length, and includes the smallest British beetle, the ironically-named Nephanes titan (Newman). The common names comes from the distinctive structure of the wings, which often protrude from beneath the elytra when at rest. Most species are brown or black, and many species are found in decaying organic matter, particularly compost heaps, dung heaps, grass cuttings and rotting wood, where conditions are favourable for the fungal growth that both adults and larvae graze on.
There are three subfamilies on the 2012 British list: Nossidiinae, Ptiliinae and Acrotrichinae. Nossidiinae has just one British representative, Nossidium pillosellum (Marsham), which is found mainly in rotting elm stumps (Ulmus spp.).
Subfamily Ptiliinae includes 44 species. Several are known in Britain from very few specimens, including Ptiliolum sahlbergi Flach, Ptiliolum caledonicum (Sharp), Oligella intermedia Besuchet, and Ptilium caesicum Erichson, while Euryptilium gillmeisteri Flach is a relatively new arrival. Some species, notably Ptilium myrmecophilum (Allibert) and Ptenidium formicetorum Kraatz are associated with ant nests, but most occur in decaying organic matter of various kinds.
Acrotrichinae contains the remaining 30 species, also found mainly in leaf litter, dung, compost and fungi. Nephanes titan is a member of this subfamily, and is common in old dung heaps.
Life cycle and reproduction
Ptiliidae have a short life cycle, with an egg-adult time of 32-45 days observed for three British species of Ptinella. They can reproduce continuously under favourable conditions, with larvae often co-occurring with both teneral and fully hardened adults at different times of the year. The eggs are very large in comparison to the adult female (nearly half her body length) so only one egg at a time can be developed and laid. Thelytokous parthenogenesis is exhibited by several species, these only being known from females.
Featherwing beetles are the smallest known beetles, the majority of the species being a millimeter or less in length. The common name is derived from the distinctive structure of the wings, which are believed to function primarily for passive flotation like the ciliate seeds of dandelions. These wings are usually folded out of sight under the wing covers or elytra, which are shortened and truncate in some genera. However, in preserved specimens the featherwings often project beyond the apex of the elytra and aid (with the minute body size) in the recognition of this family.
Ptiliidae is a family of very tiny beetles (including the smallest of all beetles) with a cosmopolitan distribution. They are colloquially called featherwing beetles, because the hindwings are narrow and feathery.
There are approximately 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.
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. Ptillid wings are feathery due to the much higher effective viscosity of air at small body sizes, which makes normal insect wings much less efficient. Unlike other small insects with feathery wings, such as parasitic wasps like fairyflies, ptillids do not fly using a clap and fling motion, but instead fly using a figure of eight pattern where the wings clap at the apex of the upward and downward strokes. They are capable of flying at speeds comparable to their larger relatives.
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.
Many species (e.g. in Ptinella, Pteryx, and Ptinellodes) are polymorphic, with two morphs so distinct that they appear to be different species or genera. There is a normal morph with well-developed eyes, wings and pigmentation, and also a vestigial morph in which these features are reduced or lacking. The vestigial morph is more common, making up 90% or more of individuals.
Life Cycle (Back to Top)
Under favorable conditions Ptiliidae appear to reproduce continuously; larvae often are found together with both teneral and fully hardened adults at different times of the year. Only a single egg is accommodated and matured in the abdomen at a time, and this egg is nearly half the female body length (Dybas 1978). The developmental period seems to be short; mean time from egg to adult in three British species of Ptinella was 32 to 45 days at 20°C, with three larval instars (Taylor 1975). Larvae are pale, slender, and active (Dybas 1976). The pupal stage has been described adequately only for Acrotrichis fascicularis (Hinton 1941).
Feeding and diet
Most species of feather-winged beetles feed on fungi.
Other behaviours and adaptations
Some feather-winged beetles are blind and most live under bark in forests and woodland. Not surprisingly they go unnoticed.
Danger to humans
Tiny beetles like this are usually the cause of cyclists’ ‘fly-in-the-eye’ condition. Most flies have no problems avoiding humans but some slow-flying beetles get caught. Cyclists sometimes get them stuck in their eyes, especially in the evening when most beetle dispersal occurs.
The feather-winged beetles are the smallest of all beetles and possibly of all insects.
Identification
Feather-winged beetles are distinguished by their feather-like wings.
Habitat
Feather-winged beetles live in forests and woodlands and heath.
Distribution
Feather-winged beetles are found in eastern Australia.
The featherwing beetles (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 0.34.0 millimetres. They are colloquially called featherwing beetles, because the hindwings are narrow and feathery. Around 600 species have been described worldwide, thereof 87 species in 87 genera in Europe. Both beetles and larvae live in rotten wood and decaying plant matter. They are mycetophagous and feed on spores, mainly of mould, but also of higher fungi.
