Another local amphipod present on the sandy beach, M. californiana is easily identified by longer antennae and a dark butterfly-like pigmentation along the dorsal axis. These amphipods participate in large amounts of kelp removal when in large numbers. Their size range varies with age, but can grow from 15mm to 20mm. Sands Beach is not known to have high counts of these beach hoppers, though a large patchy group is known to occur. Their activity is pronounced during night, when they are foraging and colonizing new wrack. These amphipods have large aggregations of phoretic mites and nematodes. Their diet, besides kelp, consists of scavenged arthropods and cannibalized amphipods.