In Fine Featherwings

Is it a bird? Is it a plane? No, it’s a beetle! In a similar fashion to birds, featherwing beetles, of the family Ptiliidae, are equipped with long feather-like appendages, earning them their distinctive denomination. These remain tucked covertly under the wing cases, coming out to guide them on their merry way, as appropriate. Since two finely-decorated feathers would be relatively useless for conventional flight, featherwing beetles are thought instead to simply drift in the wind. The feathers would catch air currents and carry the beetle away, much like the seeds of a dandelion or the thumb of a confused hitchhiker.

Posthumously showing off those fine appendages.

‘Why do I never see these gracing my garden or terrorising my picnic,’ you ask? Don’t take it personally; among featherwing beetles are the tiniest beetles known to science, ranging in size from 0.3-4.0 mm! Just spotting them can be a challenge*, let alone recognising them for their pretty plumage. This miniaturisation does, however, come at a cost.

Three featherwing beetles in a Tullgren funnel extract (alongside a few springtails and mites).

If you’re anticipating a heart-breaking tale, take solace in the fact that this beetle’s heart probably will not break – since many don’t have one! To compensate for their small size, many featherwing beetle species have rid themselves of the “unnecessary bits” like a heart and parts of their digestive system. Given the complex nature of the nervous and reproductive systems of beetles, however, we needn’t worry about them getting any smaller**.

Featherwing beetles are often found in rotting organic matter, such as the decaying wood of juicy, juicy rot-holes in veteran trees. Given the cryptic nature of these habitats and the minute size of the beetles, they truly are the masters of secrecy and hide-and-seek, remaining hidden from even most entomologists. The smallest examples of featherwing beetles, belonging to the genus Nanosella, are often found in the tiny spore tubes of polypore fungus, with other species preferring anything from leaf litter to alligator nests.

The perfect home for many of our feathery friends.

Much of the recent research on featherwing beetles has focussed on describing their many species, with 600 described and many more to come. With so many undescribed specimens sitting in wait in museums and collections across the globe, and likely many more species remaining unfound, there’s no telling exactly how many species of featherwing beetles there actually are.

Other research surrounding featherwing beetles largely focuses on them as an example of extreme miniaturisation or their fascinating reproductive system. Rather than throwing out tens or hundreds of eggs per year like many other insects, featherwing beetles produce only one egg at a time. How unproductive! Actually, these eggs are usually half the length of an adult beetle, making them quite a burden to bear. If that isn’t odd enough for you, females of many species can reproduce parthenogenetically, meaning they’re churning out clone after clone of themselves into the world, much like many aphid species and Adam Sandler films.

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Tullgren funnels (an incandescent light over a mesh-based sample caddy with a funnel leading to a liquid preservative) are probably among the easiest methods for extracting and studying featherwing beetles.

My first encounter with featherwing beetles during my MRes completely amazed me, so hopefully they’ve captured your imagination too! If you’d like to know more, the University of Florida’s ‘Featured Creatures’ page is very informative and, of course, scientific literature contains boundless accounts of these magnificent midgets. Keep your eyes peeled (and maybe zoomed in) and maybe you’ll see one someday!

* The pictures you can see were taken at 60X magnification!

** These take up a good amount of space and are an evolutionary obstacle to smaller size.

Some papers about featherwing beetles:

Dybas, HS (1966). Evidence for parthenogenesis in the featherwing beetles, with a taxonomic review of a new genus and eight new species (Coleoptera: Ptiliidae). Zoology 51: 1152.

Grebennikov, VV; Beutel, RG (2002). Morphology of the minute larva of Ptinella tenella, with special reference to effects of miniaturisation and the systematic position of Ptiliidae (Coleoptera : Staphylinoidea). Arthropod Structure & Development 
31 (2): 157-172.

Polilov, AA; Beutal, RG (2009). Miniaturisation effects in larvae and adults of Mikado sp. (Coleoptera: Ptiliidae), one of the smallest free-living insects. Arthropod Structure & Development 38 (3): 247-270.