I'm looking to identify a sci-fi book.
This sounds like In Death Ground (1997) and The Shiva Option (2002) by David Weber and Steve White, part of the Starfire series.
In this story Humans who are allied with "Orions" (cat-like aliens) and several other species (including "Gorms", sort of troll-like, and Olphiuchi, roughly bird-like) encounter and fight against an insectile/arachnid species known as "Bugs". The bugs are implacable conquerors, who reduce conquered species to food animals. They also seem, at first, to have almost unlimited resources.
Several species not previously known to humans are encountered during the second book, and become allies of the humans against the Bugs. All humans are part of a single interstellar government.
There are multiple classes of warships and freighters, similar, in roles and names, to naval ships circa WWII. Ships go from one system to another using wormholes known as "warp points" that must be searched for. Most systems have only a small number of warp points, less than 10, some only 1 or 2. There are different numbered "types" of warp points. Some are detectable only from one end. Fortress space stations often defend wormholes, taking advantage of the disorientation felt by crew and computers on passage, and by the need for all ships to appear at a known location. Minefields accompany such fortresses. Fortresses are known as OWPs, and come in several numbered types.
Combat uses a combination of missiles and energy weapons. One type of energy weapons is known as "primary beams" in what seems to be a nod to the much earlier "Lensman" novels of E.E. "Doc" Smith.
Humans and their allies never succeed in communicating with the Bugs, but we get a few scenes from the Bug PoV, in which they refer to their most populous and developed star systems as "Systems that must be defended".
There are appearances by and references to characters who have been major characters in books set earlier in the series, and minor characters become more important in books set later.
All the items listed by the OP match except that the spider-like "bugs" are clearly antagonists, not protagonists
The "starfire" series grew out of backstory for a space fleet wargame that Weber had worked on.
