Out of the four Cafius species on the beach, Cafius seminitens is the largest ranging 8.5mm to 14.5mm. C. seminitens is the second most common Cafius on the beach, next to C. canescens. During summer monthes, these beetles can be found commonly at night along with C. canescens, in wet ot dry kelp, across all beaches except Goleta Slough Beach and closely associated areas. These black beetles typically contain bright pewter (silver) hairs that run vertically down their body. This feature allows them to be distinguished from C. canescens, a smaller species of Cafius, generally confused with C. seminitens. C. seminitens is the most robust of the Cafius genus and one of the most aggressive. Their diet consists of the eggs and larvae of flies that are found in decaying algae. They are also known to consume moderate sized amphipods. They typically spend their time predating and crawling under the washed up kelp, though can be seen more active nocturnally. C. seminitens will fly short distances between wracks to escape predation of colonize kelp wrack, but are also more likely to blend in with beach detritus by remaining still. Phoretic mites and nematodes have been known to occupy their wings and elytra in large numbers and moderate frequency. Cafius seminitens sometimes carries a species of parasitic fungus, Laboulbenia philonthi (described in Thaxter 1893), which has a very low impact on the actual health and fitness of their host. Overall, Cafius seminitens is perhaps one of the most abundant arthropod predators, providing a unique opportunity for research. Past research has included descriptive taxonomy (Orth and Moore 1980), larval descriptions (James, Moore and Legner 1971), phylogeny (Jeon, Song and Ahn 2011) and unique adaptations (Topp and Ring 1988).