Frogs

A bipedal species with four arms (two larger, two smaller) ‘Frogs’ are not actually amphibians. However, their head shape is distinctly frog like, to the point that upon being shown examples of the Earth based species even the Frogs remarked on the uncanny resemblance.
The frogs are a long lives species that goes through sequential hermaphroditism during their lifecycle. Frogs are born in large batches and quickly mature into large, strong bodies with incredibly dim wits. In this stage, ‘Worker’ Frogs are used as a slave workforce for the benefit of the empire. They remain in this stage for a number of years naturally, but Frog society often uses drugs to keep most Worker Frogs artificially in this state to keep them as useful labor.
Otherwise, Workers mature into more intelligent and adventurous ‘Journeyman’ frogs, becoming male. These serve the same role as adults do in most other races, either overseeing the workers or leading armies or pursuing knowledge. It is very common for frogs to use this period of their life to go out and see the galaxy, while they still can.
Frogs that survive long enough metamorphize into Matrons, becoming female. Matrons breed with younger Frogs to produce offspring. It is these Matrons that rules the Frog empire, and traditional they are supposed to return to the core worlds during this time to establish a Brood. Socially, you can think of a Brood as a mafia with the Matron at the top, possibly with daughter Matrons serving under her if she lives long enough.
In addition to this, frogs have a unique biological quirk regarding nervous system and fat storage. Simply put, their brains never stop growing. It is for this reason that Frogs start dim and grow more intelligent over time. Unlike other races, the Frog's brain becomes increasingly decentralized and grows throughout their body like fat deposits, though their vital functions are always supported by the protected ‘life brain’ that they are born with. This enables frogs to have very detailed, long memories. However, the fate that all Frogs eventually suffer is that the growth of their brains overcomes the ability of their bodies and organs to support them. Older Matrons make heavy use of cybernetics and medical equipment to extend their lives, but eventually even that fails them. Max frog lifespan can be up to 600 years this way, though only a few have ever reached it.
Between their long lives and large birthing numbers, Frogs are the most populous spacefaring race, and one that can afford to use meatgrinder tactics of throwing waves and waves of workers at the enemy. Empathy is a foreign concept to Frogs, because life is cheap and survival is an accomplishment to be boasted.
The frog lifecycle used to be only a couple decades from start to finish, but with advanced medical technology and social engineering they have stretched the whole thing out. They always lay eggs in large numbers, so their population naturally explodes based on the number of Matrons in existence at a time, which they now have a much tighter control over than they used to in order to keep their population under control.
Nowadays, only a small number of drones are allowed to transition into males. The rest are kept on drugs that keep them as stupid animals for their entire lives, a permanent member of the manual workforce. They never developed much need for automation, because they have a neverending supply of slaves they have to do something with. Life is inherently cheap for Frogs, and they naturally accept that as fact in regards to drones.
The Male phase, that used to last only a couple decades, now lasts for nearly a hundred years before they finally start becoming Matrons. They would slow it down further, but because the transition is based on brain growth there comes a point where slowing it down any more turns them into alzheimers patients. And at this point they are males instead of drones, and thus 'people', so thats not okay.
The distinction between the stages of life are reflected in the technology they use. Despite having actually very advanced technology, the vast majority of what the Frogs use is extremely cheap, because it is built for use by Workers. Most Frog ships are well designed but ultimately cheap and crude, relying on such weapons as heavy lasers and torpedos. Though, after encountering humanity, Frogs have adapted the concept of Kites as a military weapon on these ships. These ships are largely considered disposible, with only a handful of Journeyman Frogs onboard.
"Real" Frog warships are much more advanced, and easily recognized as such. It is these ship which carry the Frog's version of a weapon known as the Krylon Beam, a technology only otherwise seen on Intercessor ships and whose exact nature still eludes human science.
In person, you can recognize Journeyman Frogs by their expertly made hardsuits. Worker frogs, in comparison, wear vacsuits made out of a leathery substance that appears to be processed from the skin of dead Frogs.
You should expect to never see a Matron.