Ten facts about rove beetles (Staphylinidae)
This edition of ten facts is courtesy of Stelios Chatzimanolis - he's an evolutionary biologist and entomologist, working at The University of Tennessee at Chattanooga. You can learn more about Stelios at his website, blog or follow him on twitter.
Here are ten facts about some pretty amazing beetles:
1. Rover beetles do not look like other beetles. Unlike most beetles, rove beetles have short fore wings (elytra) and part of their abdomen is exposed. Superficially they look like earwigs but they never have the pincers present in earwigs. Most rove beetles are 2-8mm long but few of them are giants.
2. But they can still fly. Despite the short elytra, most rove beetles have a functional set of hind wings that is not shorten. That means, it takes the skill of an origami master to fold the full length hind wings under the short elytra.
3. There are about as many rove beetles as all vertebrates together. The family Staphylinidae is the largest (or second largest if you are talking to a weevil systematist) family of beetles. The latest count of described rove beetles bring their numbers to just over 60,000 (Newton personal communication), just a bit lower than the latest count for vertebrates.
4. New species, new annexations. Hundreds of new rove beetles are described every year, but the family has grown in size also by incorporating other families. The rove beetle subfamilies Pselaphinae and Scydmaeninae used to be their own families and a very recent paper by McKenna et al. points out the Silphidae should be part of Staphylinidae as well.
5. Rove beetles have been around for a long time. The oldest rove beetle is known from the Triassic of Virginia (~210 million years old) and most rove beetle subfamilies are thought to have originated in the Jurassic.
6. A lot of rove beetles are not small and brown. Entomologists working with rove beetle are often teased that they are fond of small, brown (or black) beetles that are difficult to find and identify. And while most rove beetles are tricky to identify many have spectacular color and impressive size.
7. Some things change while others stay the same. There is a lot of morphological variation in the body form of different rove beetles subfamilies. At the same time, some lineages of rove beetles have been pretty resilient to morphological change. For example, the genera Octavius and Phloeocharis have remained morphologically unchanged for the last 90 million years, a phenomenon known as bradytely.
8. Chemical factories R us. Most rove beetles have abdominal glands that secrete chemicals for defensive purposes or for chemical mimicry (see 9. below for more on this). Despite the vast diversity of rove beetles, just a handful of studies (e.g. here, here, here and here) have been conducted on the composition on these chemicals or the chemical ecology aspect of their behavior. Their flexible abdomen (due to the short elytra) is capable of moving in many different ways aiding in the dispersal of these chemicals.
9. Myrmecophiles and termitophiles. There are probably thousand species in the subfamilies Aleocharinae, Pselaphinae and Scydmaeninae that are inquilines of ants, termites and other social insects. Although in some cases rove beetles live commensally (= true inquilines) with social insects, in other cases the rove beetles will feed on the larva of social insects or the social insects themselves. For a great article on the relationship between rove beetles and social insects see this blog post by J. Parker and T. Eldredge.
10. Rove beetles need you! There are still many thousand species waiting to be discovered and described either in the field or in museum collections, not to mention that we practically have zero knowledge of their ecology and behavior and natural history. Despite the huge number of species, the number of entomologists (at least in N. America) working with rove beetles is very small.