The second time i've seen it here in a week. Last time was in the evening. (I was there once in between where it was not present) both times it did not move
Planted tree, leaves smell like grapefruit
Indeed on milkweed.
About 1/2", on Urosalpinx cinerea (Eastern Oyster Drill).
Small flock of 7-8 of them, noisy.
Female, was laying eggs in the water.
See orange stripes on the stalk of the one in the middle; most were striped very pale orange.
AKA Lake Merritt Nudibranch. Possibly the least attractive nudibranch species I've seen, and missing some cerrata too. Teeny, sort of resembles Eubranchus rupium. Certainly the grossest quality water! Video: http://youtu.be/8o0R1MDiZMo
Directions for future hunters:
Park at the Lake Merritt Boating Center ($5 on weekends). Their dock is public and easy to access. Found the nudibranch 6" below water surface between densely packed mussels on the west side of the longest floating boat rental dock, at the cleat between the two pontoon boats. That's about 2/3 of the way to the end. Look for the small orange-striped anemones, Diadumene lineata (white tentacles), which some sources say this nudibranch eats; other sources say hydroids. Most of this dock seems to be anemone-free except for the west edge.
Wash hands thoroughly afterwards (yes Nudibranch MOM!)!