Trite

The Trite is a spider variant of the Hopper. Leaps with less frequency, but at greater distances. This can make them extremely dangerous, as they could potentially leap from one side of the room to the other, catching the player off guard.

Ragling
The Ragling is a variant to the normal Trite. This version can shoot 2 magenta-colored orbiting shots (similarly to the Night Crawler) as well as leap like a normal Trite. However, as they also have the option to use their orbital shot, they do not leap as often as the Trite and rarely move directly towards Isaac.

Rag Man's Ragling
Rag man's Ragling is an alternate version of the Ragling spawned by Rag Man and Rag Mega. They behave like normal Raglings but have more health. If they were spawned from Rag Man's Head or by Rag Mega, they will leave a pile of Rags upon death, from which Rag Man and Rag Mega can revive them. If Rag Man or Rag Mega is killed before them, then they will not leave Rags behind.

Blister
A Blister is a Trite variant that has much higher health but leaps very slowly. They occasionally spawn a Dark Ball like the ones spawned by Little Horn. They spawn a Sack upon death.

Twitchy
Twitchies are a Gaper/Trite hybrid found only in. They alternate between chasing Isaac and rapidly leaping at him. They leap at Isaac 1-3 times before returning to chasing him on foot, and their leaps can target him from almost across an entire normal-sized room. Most leaps target Isaac's location, though they will occasionally attempt to leap to where Isaac is moving. They can also occasionally leap away to dodge Isaac's tears.

Their heads also occasionally twitch violently (hence the name), although this is purely cosmetic.

Trivia

 * A trite is the name of a genus of the jumping spider family.
 * Trites share the same name with an enemy in Doom 3, an enemy that leaps towards the player and has an upside-down human-like face.
 * Blisters were given a shooting animation in Booster Pack #5, based on this Steam Workshop mod by TheShadyOne.
 * Blisters originally had 54 base hp and 0 stage hp; however, this was changed in Booster Pack #5.
 * Blisters had the fifth-highest base health of all the non-boss enemies, after Dingas, Mama Guts, MemBrains, and Oobs.