Cave crawlers are Slayer monsters that require level 10 Slayer to kill. They drop a variety of Herblore related items and seeds. They are, however, poisonous, and have a fast healing rate (approximately 10 life points per second). Level 78 cave crawlers have a much higher chance of dropping herbs and seeds than the level 53 and 74.
Cave crawlers are a popular delicacy amongst the Dorgeshuuncave goblins, who cut them into fillets and serve them on a large platter. Consequently, they are weak to all bone weapons, including zanik's crossbow, which makes short work of most assignments.
Fremennik Slayer Dungeon (level 53 & 74) - Recommended for Slayer tasks and slaying in general. Many in one open space. (Fairy ring A•J•R)
Lumbridge Swamp Caves (level 53 & 74) - Recommended for Slayer tasks for the close proximity to a bank and for the fact that they drop white berries and rare herbs quite frequently. You need a light source, and a tinderbox and spiny helmet (or slayer helmet) are recommended. There are three cave crawlers at this location, and they respawn very quickly. Note: A rope is required for first-time entry, unless you've started The Lost Tribe quest, in which case these caves can be accessed from the Lumbridge cellar. (The entry must be opened with a pickaxe the first time, but is just to the south after you enter the cave goblin tunnels.)
When fighting the level 53 crawlers, a player shouldn't need much food; about 4-6 cakes (798 health healed each) should do for a player with a decent Defence level if an antipoison is consumed immediately upon being poisoned. The level 74 and 78 crawlers are a tougher challenge and require good healing abilities. Cave crawlers are great temporary training for mid-high level melee players. With heavy armour, a 2h sword and revolution activated, they are easy kills.
Cave crawlers poison fairly often so it is advised to use anti-poison potion when fighting them, or prevent being poisoned (for some time) using a super antipoison or using the Oo'glog thermal bath prior to engaging in combat. Their poison is fairly powerful and will initially cause 80 damage. Even high level players are suggested to bring at least one antipoison, as the poison can kill you if you're not careful. Equipping one's best defensive melee gear and using Super defence potions can minimise the chance to take a hit and be poisoned, which can reduce antipoison usage.
Note: For DIY or low-level players fighting cave crawlers in the Fremennik Slayer Dungeon, who you could easily make antipoisons by obtaining the marrentill and vials of water as drops, killing a unicorn located near the entrance, and using a pestle and mortar to grind the horn into unicorn dust. However, due to the cheap price of antipoison on the GE, it may be easier just to buy some before entering the dungeon.
The level 78 cave crawlers are in a good spot to use a dwarf multicannon, it is recommended to use Protect from Ranged with this strategy because you will be attacked by many of them at once. However, a Slayer task may use up to around 1,500 cannonballs to complete using this method, and the prayer will not prevent poisoning.