Hivers

Human spacers call this species "Hivers" (or even more informally, "Bugs") because of their resemblance to the countless insect species found on Earth. The Hivers refer to themselves as "The Children". Size notwithstanding, Hivers do have many features in common with terrestrial insects, especially when it comes to social organization and physical appearance. Nonetheless they are a fully sentient space-faring race.

Favouring expansionist policy, the hivers have an explosive population growth rate compared to the other races, and can afford to build many more colonizers for new colonies than other races because they can send colonizers with outdated sublight engines through their gate network. Because they do not require a complicated FTL drive present in most of their ships, they have a noticable advantage in the number of weapons present on their normal ships, and as a race they tend to have much more durable ship armor than the other species.

Because you can move your ships instantly, you can use spare gate capacity to swap defense fleets back to your colonised planets to repair them if they take damage on an uncolonised world. (assuming their engines aren't destroyed)

The disadvantage? Hiver ships require extra research for their sublight range to match the range of the other races' ships, and even then they travel at a crawl to planets not on their Gate Network. This means assaulting a fortified enemy planet is a many-turn marathon across deepspace at sublight speeds, risking interception, with a fleet that will have cost you a very big downpayment, all in order to set up that crucial gateship and bring in the reinforcements.