Dec. 02, 2014

Picture of the Week: Livingstone's Beetles

by Emma Bryce

Click to enlarge images
David Livingstone collected beetles, I presume?
That’s the question curator Max Barclay pondered recently when he stumbled upon a box containing beetles, some of which bore tags with the famous Scottish explorer’s name, at London’s Natural History Museum. The specimens are evidence that Livingstone concertedly collected beetles during his six-year journey along the Zambezi River in Africa, starting in 1858.
“What we did not know is that Livingstone’s expedition collected proper scientific specimens of beetles, and that these had survived,” says Barclay.
Before the box was discovered, curators knew of only two beetle specimens that had been sampled during Livingstone’s lengthy trip—a goliath beetle and a common flower chafer beetle (one had been found by a botanist on board). From those two, the collection has now grown to 20 specimens, amounting to 11 species. “We’ve increased the number of known Livingstone specimens by an order of magnitude,” Barclay says.
Barclay found the insects when he was cataloging specimens for the museum’s growing digital database. They lay amid unsorted boxes in the museum’s 10 million-strong beetle specimen collection (amounting to about 200,000 species), seemingly overlooked by previous curators, probably because the species aren’t new to science. Barclay suspects that no one had noticed Livingstone’s name printed in tiny letters on tags pinned to the individual specimens.
The beetles were part of a private collection owned by Edward Young Western, a lawyer whose insect specimens were donated to the museum almost 100 years ago when he died in 1924. They include the variegated golden longhorn beetle that appears in the image below.
This striking specimen (Tragocephala variegata) is common throughout the southern half of Africa. It gets its name from the long antennae—the “horns”—that can outgrow the length of its body. Many longhorn species are known bee or wasp mimics: Their stark black and yellow coloring makes predators believe they are dangerous when, in fact, they aren’t. This species feeds on baobab, mango, and hardwood trees such as African mahogany. The larvae bore into wood, which can damage food crops and commercial hardwoods. “In some cases it can be a pest, by weakening or spoiling the timbers of trees,” Barclay says.
In 2012 a group of museum scientists led by entomologist Hitoshi Takano retraced Livingstone’s expedition as part of their African field research. They collected specimens along the way, and coincidentally returned with almost all of the same species that appear in the Livingstone collection (plus many more). Comparing the older specimens with the same species gathered during the recent expedition can provide insight into environmental changes that have occurred in the region over the past 150 years.
For instance, “there was one beetle Livingstone had that we didn’t get on our expedition, and the recent expedition would have been much more thorough,” Barclay says. “It’s interesting that that species is missing, and it could mean that it’s gone”—perhaps as a result of habitat destruction, or the effects of climate change, but those suggestions would require more data to confirm, according to Barclay.
The two insect collections are now on display side-by-side at the museum, and will be for several months.


*This article was updated on December 2, 2014, to reflect the following correction: An earlier quote from Max Barclay stated that the specimens collected on the Livingstone expedition had increased by "orders of magnitude." More accurately, they have increased by "an order of magnitude."  
About Emma Bryce

Emma Bryce is a freelance science writer whose articles have appeared in publications such as The Guardian and Audubon. Follow her @EmmaSAanne

The views expressed are those of the author and are not necessarily those of Science Friday.
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