Skulltula

Skulltulas are spider-like enemies that have been featured in several Zelda games.

Characteristics
Although the Skulltula's specific appearance varies from game to game, it is always depicted as a large spider with a skull-like shell. In Ocarina of Time and Majora's Mask, these foes hang from the ceiling and surprise Link by dropping down and attacking him. If Link comes too close to them, they will spin around quickly, injuring him and tossing him backwards. Twilight Princess incorporates larger Skulltulas that can crawl across the landscape, fighting Link one-to-one instead of keeping to their webs like in previous incarnations.

Akin to the Ocarina of Time version, the species seen in Phantom Hourglass and Spirit Tracks like to hang from a single strand of webbing, only after ambushing intruders. Other than that, these creatures do not have much offensive strategy. In the former, the spiders exist exclusively in dungeons, and in the latter, Link can encounter them only deep in the expanses of the Forest Realm while riding the Spirit Train. Only in Spirit Tracks do Skulltulas come in standardized colors: the rudimentary white form can be simply destroyed with one hit, while the stronger red version takes a couple strikes to dispel.

The variants seen in Skyward Sword will jump and hold onto Link if he is nearby and proceed to bite him until he breaks free. They also will constrict Link with silk shot from their mouths. They have a round purple spot on their underbelly where Link can stab to weaken and kill it.

Big Skulltula
Its likely that the first Skulltula Link meets in the Deku Tree is actually a Big Skulltula. Big Skulltula are virtually the same as the normal variety, but are considerably larger and therefore have a wider range of attack. They are less common their smaller varieties but can be defeated using the same tactics and can withstand and deal the same amount of damage.

Gold Skulltula
A special type of Skulltula that appears in Ocarina of Time and Majora's Mask is the Gold Skulltula, who drop Gold Skulltula Tokens that can be traded for useful items. In Ocarina of Time, Link collects the Tokens to free a family from a curse. Once freed, the family will reward Link if he visits them in the House of Skulltula in Kakariko Village. In Majora's Mask, Link must visit either the Swamp Spider House or Oceanside Spider House to collect the Tokens and receive his rewards.

Skullwalltula
A smaller version of the Skulltula, the Skullwalltula, also exists. It usually clings to vines that Link must climb, and charges at him if it spots him. To advance, Link can either sneak past while their back is turned, or defeat them with any ranged weapon.

Weaknesses
A Skulltula's hard, skull-shaped exoskeleton can deflect many attacks, but the arachnids are far from intelligent, and often leave their defenses open by exposing their soft underbellies. In order to attack the Skulltula with his sword, Link must wait for this opening; otherwise, the Skulltula will counterattack with its spin attack. If Link is impatient, he can attack the creature right away with his Bow, which will pierce its armor and award the hero with a swift victory.

Sword Tactics of Twilight Princess
Skulltulas in Twilight Princess seem to be somewhat more intelligent than their previous incarnations, because they actively block Link's frontal attacks and do not expose their soft underbellies except right before they attack (as opposed to their counterparts from previous games, who exposed their weak point seemingly at random). When a Skulltula momentarily rears back before attacking Link, he can counterattack the deadly arachnid by slashing it with his sword before it launches its attack, or he can dodge the spider's bite attack and hit it while it's recovering. Link can also defeat Skulltulas by first stunning them with a Spin Attack and then finishing them off with an Ending Blow. The Hidden Skills Link learns during his adventure are also useful when engaging Skulltulas. Link can use a Shield Attack to knock the insect off balance, giving him a chance to attack, or he can use a Back Slice to circumvent its defenses entirely while attacking its vulnerable abdomen. It is worth noting that if Link sheathes his sword immediately after defeating a Skulltula, he will sheathe it with a flourish, much like he does after defeating a boss.

Super Smash Bros. Brawl
Skulltulas appears as a sticker in Super Smash Bros. Brawl.

Trivia

 * Interestingly, in Ocarina of Time and Majora's Mask, the Skulltula is one of the few enemies that is sometimes cloaked in invisibility to the naked eye. Use of the Lens of Truth is sufficient in these circumstances to flush these enemies out of hiding.
 * In Majora's Mask, the use of the Hookshot is no longer effective against a Skulltula's hard skull as it was in Ocarina of Time.
 * In Phantom Hourglass, the Cubus Sisters are deathly afraid of these spiders when walking with them on the Ghost Ship; their screams not only prevent them from progressing forward, but alert nearby Reaplings to Link's position.
 * In Twilight Princess, there are two types of Skulltula: a white and an orange one. The orange one can only found in the Forest Temple.
 * The name Skulltula is likely a portmanteau of "skull" and "tarantula".