Thinopinus pictus is the largest rove beetle within the kelp wrack, ranging around 18mm to 20mm. These beetles are wingless and have a sandy appearance that allows them to blend in with the beach. T. pictus is a very aggressive ambush and active predator, feeding on most of the arthropods under kelp wrack. These beetles are most commonly found at night during summer months, and can be found on Elwood Beach and Sands Beach. Meetings between conspecific individuals may result in aggressive attacks, resulting in injury or decapitation.