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The Largest Family in North America 

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Margaret Thayer

Entomologist

The Field Museum of Natural History

Asked what he could infer about God from nature, British biologist J.B.S. Haldane replied that the deity must have "an inordinate fondness for beetles." Margaret Thayer, assistant curator of insects at the Field Museum, spends her time studying just one family, the rove beetles, or staphylinids, more than 48,000 species of which are known so far. All the vertebrates combined--fish, amphibians, reptiles, birds, and mammals--amount to only about 50,000 species.

Harold Henderson: Why have beetles been so successful?

Margaret Thayer: One reason is probably the wing covers protecting the adults' flying wings. They can dig around in dirt or logs, then pop out their wings and fly off to another spot. Most insects that undergo a full metamorphosis can't do that.

HH: So beetles have access to more different habitats?

MT: Yes. And rove beetles are kind of superbeetles--they usually have short wing covers and are long and skinny compared to most beetles. This leaves their abdomens exposed, enabling them to be more flexible and get into tinier places than other beetles.

HH: Are rove beetles the largest family of beetles?

MT: In North America they're the largest family, but worldwide they may be second to weevils.

HH: Just a few years ago you found two new species south of the city in the Palos Hills area, right?

MT: Yes, last year I published the formal description of one of them, Xylodromus suteri, which occurs across the eastern U.S. and in Mexico. They live in tree holes, but we don't know what they eat there--probably tiny insects or worms.

HH: The number of humans studying rove beetles can hardly be proportional to their numbers. How many serious rove beetle taxonomists are there in the world?

MT: There have been annual meetings of staphylinid workers for the last 19 years, started by East German workers when they had difficulty traveling elsewhere. The 2004 meeting was attended by around 40 people, mostly taxonomists, but another 20 or so of us missed it.

HH: Is there some tension between working on the specimens already available and going out in the field to collect more? Which is the priority?

MT: Both are really important--there's lots of valuable unstudied material in collections, but also many things that have never been collected before, sometimes in habitats that are disappearing. And there's lots of library-type work, too. Al Newton, associate curator of insects here (and also my husband), has been cataloging all the described species of rove beetles and their relatives in a computerized database, part of which is up on our Web site [www.fieldmuseum.org/peet_staph/index.html].

HH: As I understand it, you spend more time than most researchers trying to get the higher-level genus and family classifications right, as well as identifying new species.

MT: Yes, we both work on that, and the Field Museum is a fantastic place for such work. It has one of the two best collections of rove beetles in the world (the other is in the British Museum), and it has an excellent library, which is very important. One part of taxonomic research and cataloging is to find the oldest names given to species or groups. Often they've been described under different names, and you have to figure out what's what.

HH: Meanwhile new species keep being described?

MT: You bet. During the 20th century the average number of new rove beetle species described each year went from about 200 to 400, but in the last few years it's been over 600 a year. There's no end in sight.

HH: And is the study of their natural history--how they live, what they eat--keeping pace?

MT: It's being pursued actively, but you need to have the taxonomy figured out to some extent in order to report usefully about their natural history--so you can say which beetle species you're discussing. Knowing about their natural history can feed back and help you do a better job of understanding later discoveries. For instance, you might find that one species has a special kind of funny mouthparts and feeds on the spores of fungi. Later on if you find museum specimens of another species with similar mouthparts, you'd have a clue as to what they eat too, and might have a better chance of finding more in the field.

HH: Now you're involved in a long-term project collecting and classifying rove beetles in the far southern hemisphere. Why there?

MT: It's a really underexplored fauna, for starters, but our justification for the National Science Foundation grant that supports the project was that many groups of staphylinids have species in at least three of these areas--Chile, South Africa, Australia, and New Zealand--and nowhere else. We want to study them to figure out how this happened and whether it's part of a pattern involving other groups too. Did they evolve before the breakup of Gondwanaland [the prehistoric continent joining South America, Africa, India, Australia, and Antarctica] starting 150 million years ago? Or evolve later and then disperse across the oceans somehow? Or disperse southward from the northern continents? Or get separated by a possible expansion of the Pacific Ocean? Besides learning about the beetles' evolutionary history, we'll increase knowledge of these southern temperate habitats, many of which are under serious threat.

HH: What would the world look like if all rove beetles were to disappear?

MT: Rove beetles are a huge component of terrestrial ecosystems (except deserts), and yet they're basically invisible. I suppose things they eat--decaying wood, fungi, carrion, dung, fleas, lice, maggots--would pile up. And animals that eat them would suffer, although we don't have much information on what those are. Staphylinids undoubtedly serve as kind of a glue in the food webs of their ecosystems, but we have lots to learn about what bits they're gluing together.

Art accompanying story in printed newspaper (not available in this archive): photo/Lloyd DeGrane.

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