This is a fully grown
G-Type Young, which is essentially the product of a G-Embryo that has rejected its host for gestation due to DNA incompatibility. The adult has an interesting characteristic as it becomes a carrier for even more
young, spewing them forth from its mouth. Whether these offspring also have the ability to grow into adults is unknown.
You fight this creature in close quarters, and with its young crawling across the floor you have multiple targets to deal with. The best strategy is try to ignore the smaller offspring and just focus your attention on the adult mother, unloading your most powerful weapons into it until it's a pile of goo. The
Shotgun or the
Grenade Launcher are the best weapons to use in this fight.