Hex-at-Legs

The Hex-at-Legs (internally known as Hex Long Legs) is a species of arachnorb that appears in Pikmin Eco. It appears as a later boss in the "Rocky Route" cave in Cloven Gardens, only accessible after unlocking the Rock Pikmin. Unlike other species of arachnorb, this species has six thin legs for locomotion, which gives it its name, with an almost metallic skin on much of its abdomen. It also has a larger, flattened area attached to its abdomen, giving it a top-like appearance. Upon dying, only its legs disintegrate, leaving only the abdomen behind to be carried and collected, suggesting that it's not apart of its actual body.

Like the Emperor Bulblax, the Hoverpack is required in order to fight it.

Strategy
Compared to most other arachnorbs, but like the Man-at-Legs, it is incapable of stomping onto Pikmin thanks to its much smaller feet. It carries its abdomen higher off of the ground, making it unreachable. After a while, it will climb up the walls and move around on the ceiling, completely out of sight except for its shadow. When a leader or their Pikmin are underneath its shadow for long enough, it will drop down and slam onto the ground, causing a tremor to occur which can briefly paralyze the leader if they're still on the ground.

After it does this though, it will briefly get stuck upside down, leaving it vulnerable to attack until its legs turn around and it can lift itself off of the ground. After this, its flattened body will be upside down, making it impossible to throw any Pikmin onto it.
 * Note: Yellow Pikmin and Winged Pikmin can still reach its vulnerable abdomen while its flattened end is right-side up, able to cause extra damage to it. This can't be done when the flattened end is to the ground, however.