The Elect Saga : Incursio (Book 3)
by Drew Wagar
"The Swarmers, an intelligent race of space-faring insectoid-like creatures, have always existed on the edge of inhabited space. Now, Swarmer starcraft, powerful, fast and dangerous are invading TradeCon space and nothing seems able to stop them. With star systems falling to the invaders on a daily basis, a desperate plan is hatched to deal with the aliens once and for all."