Hydralisks counter mutalisks and banshees. Hydralisks in large numbers also counter phoenixes. They are, however, relatively fragile and are inefficient against large numbers of armored units.
Hydralisks have a melee attack in addition to their normal ranged attack, but it does the same damage as the ranged attack. The melee attack is not cosmetic, as it has the advantage of not triggering point defense drone lasers and not being affected by sentry's guardian shield.
Hydralisks work well paired with roaches, the hydralisks dealing damage while the roaches absorb it. A combination of roaches and hydralisks can defeat a combo of zerglings and mutalisks.
Hydralisks can excel against void rays, given the starship's weakness to mass units. Burrowing for a short time to cause the void ray's attack to lose its charge, then resume attacking is the best idea against void rays.
In the campaign mode of Heart of the Swarm, hydralisks can transform into either lurkers or impalers after completing the appropriate evolution mission. Their visual design changes accordingly.
Upgrades and Abilities
Temporarily increases hydralisk attack speed by 50%. Cannot be autocast.
Hydralisk aggression inhibited by cerebral cortex. Can enable hive mind to trigger impulses directly. Upon command, attacks frenzy for limited period. Cortex requires recovery time after use. Limbic system fragile.
Hydralisk carapace evolved primarily for offensive role. Thin, hollow. Allows increased movement potential at cost of fragile structure. Possible to evolve ancillary carapace, redundant plating. Will increase protection. Hinder exoskeletal rupture.
Spine projectile, effective. Few alterations made since assimilation of slothien urticating bristles. Grooved spines, common evolution on battlefield. Can be introduced directly into hydralisk template. Will increase aerodynamic properties of spines, allow hydralisk to attack distant foes.
The hydralisk den and hydralisk strain are exclusive to Kerrigan in Co-op Missions. Kerrigan also has access to the lurker and lurker den. Additional upgrades for the hydralisk and lurker become available when Kerrigan reaches Level 6. Frenzy is also autocast. Dehaka has the ability to produce primal hydralisks, which can evolve into impalers or primal mutalisks.
↑Correct. It really is the melee attack animation. :) But the damage is the same with the range attack. Cydra. 2009-04-21. HYDRALISK HAS MELEE ATTACK!!! (seriously). Battle.net StarCraft II General Discussion Forum. Accessed 2009-04-21.