Spines Crawlers are one of the few infested structures that is offensive in nature. They posses great range and a strong attack that will easily cause a careless player to lose lives or die. Thankfully, Spine crawlers are very uncommon and appear only a few times in each campaign. The best ways to deal with them are Cloak, long range weapons and skills, or a tank with high armor, preferably Kinetic Armor. Flares and the Recon's Laser Designator also make for great ways to spot spines before they spot you. Spine Crawlers have high armor so it is important to use weapons that perform well against armored targets or ignore armor altogether.
Spine Crawlers sometimes appear during the Nydus Worms Mission. They guard some of the worms. Be wary as they can damage and quickly destroy any Reaper Drones that your Recon might send out to attack the worms.
Spine crawlers will spawn randomly in certain areas of the map during Chapter 1. They can typically be found in the area around Ramirez, and between the northern bridge and the Communications Tower. Sometimes they will appear on elevated terrain, and all will ambush careless players. Best bet is have the Flamethrower move in front to absorb the initial blows. Recon or Forward Observer flares can light the crawler up for the rest of the team to destroy. No new spines spawn after chapter 1.
A larger, much more powerful strain of spine crawlers are one of the primary attacks used by Hades. The massive creature will spawn them at regular intervals; they boast much higher health, attack speed, and damage than the smaller versions. Best to clear them out with high skills or weapons like the Stinger MK-3 as quickly as possible. Other than the battle with Hades (First Form), the Spine Crawlers do not make an appearance in this campaign.