The smallest known beetle – and the smallest non-parasitoid insect – has a body length of 0.325 mm, according to entomologist Dr Alexey Polilov of Lomonosov University.

This tiny insect, scientifically known as Scydosella musawasensis, is the only species in the featherwing beetle genus Scydosella.

It’s morphologically characterised by its elongated oval body, yellowish-brown coloration and antennae split into ten segments.

The species was first described in 1999 from several specimens found in Nicaragua.

According to a new study published online this week in the journal ZooKeys, the smallest examined representative of Scydosella musawasensis has a length of 0.325 mm.

“Not able to precisely measure its size because of the preserved Nicaraguan specimens being embedded in preparations for microscopy studies, I used new individuals, collected in Chicaque National Park, Colombia in early 2015,” Dr Polilov explained.

The measurements were made using specialized software from digital micrographs obtained under a scanning electron microscope.

“Measuring of ten specimens of Scydosella musawasensis has shown that the smallest of them has a length of 0.325 mm, the largest has a length of 0.352 mm, and the average length is 0.338 mm. The body width is 0.098 to 0.104 mm,” Dr Polilov wrote in the ZooKeys paper.

“Thus, the smallest beetle and smallest known non-parasitoid insect has a body length of 0.325 mm.”

The size of the smallest known parasitoid insect, male Dicopomorpha echmepterygis (a parasitic wasp in the family Mymaridae), is 0.139 mm.

“The record of Scydosella musawasensis in Colombia considerably broadens the known range of this genus and species, known previously only from one site in Nicaragua,” Dr Polilov wrote.

“This record also broadens the known range of fungi colonized by Scydosella musawasensis, which was known previously only from Rigidoporus lineatus. I have collected it on Steccherinum sp.”

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Polilov AA. 2015. How small is the smallest? New record and remeasuring of Scydosella musawasensis Hall, 1999 (Coleoptera, Ptiliidae), the smallest known free-living insect. ZooKeys 526: 61-64; doi: 10.3897/zookeys.526.6531