Venusian (Yargo)

The Venusians are a species of sapient flying insectoids native to the jungles of Venus. They appear like enormous hairy bees, which can reach from two to six meters in length (the queen being even larger, at seven and a half) and dwell in hive-like cities projected to create an inner atmosphere at comfortable temperature in contrast with the scorching planetary exterior. Their mouths hide arrow-shaped tongues which can be used to impale a humanoid throat, killing the victim in a particularly brutal manner. Despite this, they don't appear to be predators, as they are known to produce and feed upon a substance similar to honey except for being more solid.

Members of this species build long cylindrical black spaceships and act with hostility towards other races. Their home world's dense, hard-to-penetrate atmosphere and their own caution that prevents them from showing up against whole enemy armadas have resulted that for many years the Yargonians have been visiting the Sol System completely unaware of the Venusians' presence, firm in their belief of being the only species with access to interplanetary travel in their area of space.

Despite their appearance, the Venusians actually evolved from human-like creatures back in the days the planet had a less extreme weather. They still retain some mammalian characteristics, including being viviparous and having red blood. For some reason (likely religious) they aspire to return to that original form, which sometimes partially resurgences in mutant individuals, although these rarely live long. Once the queen gave birth to a near perfect semi-humanoid male which survived into adulthood, the Venusians abducted females of Human and Yargonian species and planned to have them mate with him in order to give rise to a new species to populate their planet.

Behind the scenes
At the end of the book, it is very strongly implied that the entire science fiction plot was a fantasy caused by mental instability on the protagonist's part; meaning that all alien species described never actually existed in-universe.