Arachnode

The Arachnode is a member of the Unknown Family in Pikmin 3. They are small yellow and black arachnid-like creatures that are always found on their webs.

Behavior
The Arachnode spend most of its time in a cocoon state until something get traped on its web. They will then uncurl their eight legs and start moving to the location of their prey. They usually build their webs in the path of Winged Pikmin, which can result in a lot of deaths if the captains let a lot of Winged Pikmin carry items without knowing that an Arachnode's web is somewhere on their path. To kill it, the captains must throw a Pikmin perfectly on their bodies, missing it result in the Pikmin being stuck in its web.

Locations

 * 4 are found in the Twilight River
 * 2 are found in the Formidable Oak

Pikmin 3 website
"An eight-legged creature that traps its prey in a sticky web."