Pacific Science Center’s Life Sciences team just added an exciting group of insects to our exhibit area to enhance the collection we already have. What made these new insects special is the order they belong to – the coleoptera, or beetles. The beetles are a huge, successful group of insects, with over 350,000 species. Beetles can be recognized by their sheath-like forewings, or elytra, which protect the hind wings used in flight. All beetles have chewing mouthparts. Beyond that, their diet and habitats vary enormously.
Some are extremely specific, with one or a few key foods they can eat. Moneilema gigas, the cactus long horned beetle, is a great example of an insect whose body is adapted to a specific plant and habitat. Their long legs help them skirt around the sharp spines of cactus, and their slow movement and lack of flight reflect the life of an insect whose best defense if the plant they live on. Cactus long horned beetles chew on cactus, opening areas where they can lay eggs. The larvae mature inside the plant, and can be a serious pest to commercial cactus growers. Our beetles have started working their way through a nopal cactus paddle.
Meanwhile, in the water, all kinds of beetles are in action. Dineutus emarginatus, the whirligig beetles, skid along the top, often swimming in circles when they get excited. Adapted to the water’s surface, these beetles’ eyes are split, with half of each eye adapted to see through air and half adapted to see in the water.
Sunburst diving beetles and green diving beetles (genus Thermonectus) spend more of their time underwater, carrying a bubble of air under their elytra like a tiny scuba tank. Because insects breathe through spiracles in their abdomen, they don’t need air around their faces, meaning they can eat underwater. These colorful and energetic beetles are skilled hunters, often feeding on insects many times their size.
The water scavenger beetle, Hydrophilus triangularis, is safe from the smaller beetles because of its thick exoskeleton. It is free to roam about the tank, gleaning bits of uneaten food, both plant and animal.
These beetle species join an exhibit floor already rich in beetle diversity. Check out the dermestid beetles, which help the cycle that decomposes dead organisms back into the soil.
The familiar mealworms, which feed on various cereals, are really larval stage of the beetle tenebrio molitor.
The blue death feigning beetle, Cryptoglossa verrucosus, is one of our favorite exhibit insects. This desert dwelling insect rests on its back or sides, in a death-like posture that rivals our naked mole-rats in its realism. Yet they are one of the hardiest and longest lived creatures in our collection.
Rounding out our beetles, we are experimenting with a handful (not literally) of dung beetles, genus Canthon. These beetles spend most of their life cycle closely associated with dung, which they eat, roll, hide in and feed to their young. If we can display them in a way that does justice to their unusual diet, they may go out on exhibit in the near future.
