Leoniders are a fictional alien race from the Noon Universe

Noon Universe

The Noon Universe is a fictional future setting for a number of hard science fiction novels written by Arkady and Boris Strugatsky. The universe is named after Noon: 22nd Century, the chronologically first novel from the series...

 created by the Strugatsky brothers. Their homeworld is Leonida (Леонида), a planet discovered in 2133 AD by Leonid Gorbovsky

Leonid Gorbovsky

Leonid Gorbovsky is a fictional character in Boris and Arkady Strugatsky's series of science fiction novels set in the Noon Universe.-Biography:...

.

Leoniders are mentioned in "Noon: 22nd Century

Noon: 22nd Century

Noon: 22nd Century is a 1961 science fiction book by Arkady and Boris Strugatsky, expanded in 1962 and further in 1967, translated into English in 1978. It is sometimes considered an episodic novel, collection of linked short stories or a fix-up as some parts had been published previously as...

", "An Attempt to Escape" and "Beetle in an Anthill".

Appearance

Leoniders are humanoids like humans

Humans (Noon Universe)

Humans of the Noon Universe created by Boris and Arkady Strugatsky are mostly identical to homo sapiens. Humans inhabit numerous planets, but their original homeworld is probably Earth, others being populated by humans, presumably, as a result of Wanderers' manipulations.-Human Planets:The...

 but somewhat smaller.

Technological advancement

The term "technological advancеment" is not very appropriate to Leoniders since their "technology" is very different from humanity's. It is known, for example, that they live in a perfect symbiosis

Symbiosis

Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 with major forms of flora and fauna of Leonida.

Leoniders and Humans

No data available despite the continuous diplomatic contact between Leonida and Earth.