In Pikmin 2's above ground areas, you can kill enemies that just happen to be above ground. If you enter a cave though and come back out, there can be enemies that still respawn unlike most enemies after a couple of days. There are a number of reasons why this happens. One is that the enemy is one that holds a treasure. If you killed the enemy but didn't get the treasure, it will ingest the object again and you'll have to defeat it again. If you already have the treasure, the enemy will still reappear if you've beaten it anyway. Other enemies are weak ones that happen to reappear just because they were programmed to.
Here is a list of these enemies:
Valley of Repose
Awakening Wood
- Unmarked Spectralids x8 (four in a Margaret, four in a nearby Figwort)
- Female Sheargrubs (appear only for a certain amount of days then they stop appearing in respawn locations)
Perplexing Pool
- Toady Bloyster (very good if you want to get a lot of Pikmin)
- Skitter Leaves (near the Citadel of Spiders entrance and the black wooden gate leading to the Submerged Castle)
Wistful Wild
- Orange Bulborb (the one that usually holds a treasure)
- Creeping Chrysanthemum (the one that usually holds a treasure)
If there are any more creatures not listed that you think should go on this list fill them in appropriately, any dispute can be resolved on the talk page.