The Bug Collection: A Brief Tour of the Essig Museum of Entomology
Reprinted from California Magazine, UC Berkeley Alumni Association
Pete Oboyski worries about bugs eating his bugs.
Scratch that. The collections manager at the Essig Museum of Entomology, Oboyski worries about insects eating his insects—specifically, a family of beetles known as dermestids, which, should they make their way in, could reduce the museum's 6-million-plus specimens to powdery ruin. As any self-respecting entomologist will tell you, true bugs are only a subset of the much larger taxonomic class of Insecta. Indeed, Oboyski's ilk tend to be a bit pedantic on that point. “Bugs” is a colloquialism they'd squash if they could.
The dermestidae, often called skin beetles, eat skin, just as the name suggests. They also eat hair, hide, fur, feathers, and meat—basically, everything but bone. And while museum curators dread the damage the ubiquitous arthropods and their larvae can do, they also make use of them.
Oboyski points at one wall of the bunker-like space that houses the Essig. On the other side of the wall is Berkeley's Museum of Vertebrate Zoology. “The vertebrate people keep a colony of dermestids just on the other side of that wall there, to clean carcasses. They like them because they do such a thorough job of it, removing every last speck of flesh.” He says it's the same colony they've had since the museum started in the early 1900s. “They use a variety that's a little too large to get into my cases, fortunately, which is the only reason I can sleep at night.”
The tightly constructed, glass-topped wooden cases in which insects are mounted on pins are the entomologist's stock in trade. The Essig holds thousands of them, all slotted in racks on track shelving that can be moved by hand cranks. It's a vast bug library filled with row after row of meticulously preserved specimens, all organized by order, family, genus, species, and subspecies. Everything in the collection is of the phylum Arthropoda—many in class Insecta,but no few Arachnida.
Something you generally won't find in the Essig is any living insects, although on this particular day Oboyski was making an exception, hatching some Australian walking sticks in a terrarium. Most of the time, live bugs are verboten, and Pete has lights and pheromone traps set up to catch any of the little buggers that might sneak in.
“If you had told me 50 years ago that we were going to sequence DNA from these specimens, I would have said, ‘What are you talking about?' Now we do it all the time. … So that's my attitude in terms of preserving these … because I have no idea what they're going to be used for in the future.”
One of the largest university collections in North America, the Essig's regional emphasis is primarily on California, but it also expands to the Pacific Rim, including the islands of the central Pacific. Oboyski, a moth specialist who earned his Berkeley Ph.D. in 2011, has identified nine new species himself—seven from Hawaii, and two from Tahiti. The museum's namesake, Professor E.O. Essig (1884–1964), author of the seminal text Insects of Western North America, was chiefly an aphid man. (Aphids, incidentally, are true bugs, part of the order Hermiptera, which, like all the other true bugs, have mouthparts adapted for sucking juices from plants … or, in the case of bed bugs, blood from people.) Essig was one of the leaders of the California Insect Survey, which grew the collection considerably in the 1930s.
“Museum” is a bit of a misnomer in this case. The Essig is strictly a research collection, made available to scientists for all manner of legitimate study, but only open to the general public a few times a year: on Cal Day, Darwin Day, and, this year, Homecoming. That said, education and outreach are a part of the Essig's charter. Schoolchildren often visit on tours, and when they do, Oboyski will show off what he calls the “Oh, my!” collection. These are the stars of the insect world: the glorious blue morpho butterflies, bizarre walking sticks, and the giant rhinoceros and Atlas beetles, which look like they could topple walls. Indeed, pound for pound, these macrobeetles are among the strongest animals in the world.
But the oohs and aahs and occasional shrieks elicited by these specimens are only a small part of the collection's value. More important is the research role they play, perhaps especially in terms of documenting ecological change over time. To the disinterested, the Essig may seem like a mausoleum, better digitized and discarded. (And in fact, digitization is underway, in part through volunteer and crowdsourcing efforts, with about 10 percent completed so far.) But to Oboyski, the physical collection itself is a vast storehouse of information that is constantly being mined in new ways.
Think about it, he says; we now have CT scans that allow us to scan the internal anatomy. We can look at stable isotopes to study their diets and how they've interacted with the environment. We can grind them up and extract DNA.
“If you had told me 50 years ago that we were going to sequence DNA from these specimens, I would have said, ‘What are you talking about?' Now we do it all the time. Fifty years from now, I have no idea what people are going to be doing. … So that's my attitude in terms of preserving these. I want to preserve them as pristinely as possible for as long as possible, because I have no idea what they're going to be used for in the future.”
In the meantime, for those who get heebie-jeebies just thinking about bugs, it's probably good to remember that insects are crucially important to us in myriad ways, both “good” and “bad.” Insects pollinate our crops and also sometimes destroy them. They control disease but also spread it. When ecosystems are in balance, insects check each other's populations. And even those destructive skin beetles perform a crucial service: They are natural recyclers, part of life's great dust-to-dust cycle.
To give a sense of how wondrous and important the insect world is to California, and to Berkeley researchers, we asked Pete Oboyski to introduce us to a dozen or so species from the Essig's vast collection, beginning with the cutest of all, the ladybugs—which, at the risk of being pedantic, we have to point out are not really bugs at all.
The convergent ladybug, or more properly, convergent lady beetle (Hippodamia convergens),is a familiar sight in the Berkeley Hills, where large clusters of them often overwinter or carpet the forest floor. H. convergens is commercially gathered from large aggregations found in the Sierra Nevada for use as biological control—particularly of aphids, which are the beetle's primary food source. Oboyski says agriculture has changed the behavior of these beetles over time. Before water was diverted for agriculture, he explains, the aphid populations would naturally decline in the summer as vegetation dried up. In response, the lady beetles would move up into the hills. Now they tend to stay all season due to an abundance of food. “We've completely changed the dynamics of these beetles to a large part because of agriculture, which is supporting things they feed on.”
The ubiquitous crane flies (Tipulidae) are doubtless among the most misunderstood insects found in our homes. Many of us mistake them for giant mosquitoes; others believe the flies prey on the mosquitoes, calling the flies “mosquito hawks” and “mosquito eaters.” In reality, says Oboyski, “they don't feed at all as adults. And they don't live long. But they're food for an amazing number of vertebrate animals—bats and birds and lizards and anything else that can catch one will eat it. So while [the crane flies] come out in abundance, like all those baby sea turtles heading for the ocean, only a couple of them actually survive to reproduce.”
The glassy-winged sharpshooter (Homalodisca vitripennis) is a large leafhopper native to the American southeast. It is of special concern in California because the species carries a plant pathogen in its system that triggers a grapevine blight called Pierce's disease. The invasive H. vitripennis also made its way to Tahiti where, lacking any predators, the population exploded, leading to something called “the rain effect.” Oboyski explains, “They're sapsuckers, so they're drinking lots and lots of sugar water to get little bits of nitrogen, which they really need to build proteins. But most of that sap is just water, and so they need to pee.” In Tahiti, the sugar-water excrement coming from the trees was often so thick that it was like a rain shower. Luckily, researchers from UC Riverside were able to introduce a parasitic wasp to rein in what locals had taken to calling the “pissing fly.”
Probably no household pest is quite as repugnant to us as the bedbug (Cimicidae), which feeds on our blood at night. Not so long ago, Oboyski notes, bedbugs were just a fact of everyday life. “It wasn't until World War II and the chemical revolution and DDT that we were on the verge of chemically controlling them, and they disappeared for a few decades.” Now, however, they're resistant to DDT and other chemicals and are making their resurgence, much to the alarm of hotels and their guests. “I get calls from people who want to sue a hotel because they found bedbugs in their room. And the bedbugs are completely harmless. They aren't carrying any disease; there's just this connotation of being unhygienic. Whereas mosquitoes actually do carry diseases—but would anyone sue a hotel because they got bit by a mosquito? Probably not.”
When it comes time for the female tarantula hawk, the giant in the family of so-called spider wasps (Pompilidae), to lay its egg, it engages in an epic struggle with a tarantula. They're pretty evenly matched, observes Oboyski, and the stakes couldn't be higher. “If the wasp loses, it gets eaten; but if it wins, it paralyzes the spider with its sting, drags it off and buries it, and then lays its egg in [the spider].” As the larva develops, it feeds on the tarantula, carefully avoiding the host's vital organs so as not to kill it off. Although tarantula hawks are considered fairly docile, their sting is said to be extraordinarily painful. Arizona-based entomologist Justin Schmidt, best known for his “sting pain index,” calls the sensation “instantaneous, electrifying, excruciating, and totally debilitating.” Schmidt's advice: Lie down and scream.
On the other end of the size spectrum, the diminutive gall wasp (Cynipidae) grows its larvae in a plant growth called a gall. “Each gall is very specific to the wasp that laid it,” explains Oboyski. “It's the plant that grows the tissue, but somehow the wasp is telling the plant to grow this exact shape for [the wasp's] larvae. Along with the egg, they're introducing some enzymes that are turning on genes inside the plant.” But the story doesn't end there. “As if that's not enough, there are other wasps that want to lay their eggs there, too. So now you have interlopers. And then there are things like parasitic wasps that know there's some nice squishy larvae in there, and they insert a tube into the gall and lay their eggs inside those larvae. Then there are hyperparasitoids that lay their eggs inside the larvae that are inside the other larvae. And then there are things that feed on the galls outside. So a whole community arises from this tiny little wasp that caused the plant to swell up.”
Like termites, carpenter bees also burrow into wood. The valley carpenter bees (Xylocopa varipuncta) are named for California's Central Valley and are the state's largest native bees. Unlike honeybees, which were brought to the Americas from Europe, carpenter bees don't generally sting. Like honeybees, they're good pollinators. Due to the much-publicized colony collapse disorder, in which vast numbers of worker bees simply vanish from a honeybee colony, Oboyski says there has been a spike of interest in native pollinators. “We're not sure what's going to happen with honeybees, so the thinking is we'd better hedge our bets and see how we can get our native bees to provide the same services.”
Another bee that has had a lot of media attention is the Africanized bee, or “killer bee,” although less so lately. Oboyski says the Africanized bees are now hybridizing with our European honeybees, with mostly positive results, allaying earlier hysteria about wild swarms of killer bees attacking school children. “This fear that we're now going to have this more aggressive bee here is probably true, but the Africanized genes are mellowed out by the European genes.” What's more, he says, “the Africanized bees also bring resistance to some pests, like the mites that feed on the European bees. So it's actually improving their health.”
As for colony collapse disorder, Oboyski says it's still a bit of a mystery. “The leading suspects now are these neonicotinoid pesticides that [the bees] seem to be very sensitive to. But in my opinion, it's not likely to be a single factor at play. It's a species we've been managing intensely for a very long time. … They're boxed up one night in an almond orchard in California, and they wake up the next day in an apple orchard in Michigan, and it's very stressful. Neonicotinoids may just be the last straw.
“But there's been some really entertaining ideas of what happened to the bees. I remember someone saying they'd been taken up by the Rapture. They were pointing to the fact [the bees] disappear. It's not like you see a bunch of dead bees around. To me, that's not surprising because, you know, they're food. If there's a dead bee somewhere, something's going to eat it.”
California pine forests are being laid to waste as tens of millions of trees succumb to an epidemic of bark beetles, including mountain pine beetles and other relatives of the Scolytidaefamily of weevils. It may sound like an alien invasion, but it's not. Says Oboyski, “The bark beetles that are causing the problems are actually native here, and it's not that they've changed over the years. It's the way we've managed landscapes that has changed,” particularly in terms of clearcutting and fire suppression. Those practices, he says, have resulted in large monocultural stands and old decadent trees that are more susceptible to pest invasion than a “young, vigorous forest that's constantly refreshed by fires.” And, of course, drought has been an aggravating factor. “These beetles only attack stressed trees. If the tree is healthy, they get ‘pitched' out by the tarry sap they produce. But in a stressed tree that's attacked by lots of beetles at the same time, there's not enough pressure behind that pitch to push the beetles out.”
Bark beetles only infest live trees, whereas termites (Termitoidae) come in long after the tree is dead. And unlike the bark beetles, which aren't feeding on the tree but rather using it to make their nests, termites are actually eating it. To accomplish that, however, they need help. “Termites can't actually digest wood themselves, but they have this gut fauna inside that can actually convert the lignin of the plant into digestible food.” The symbionts reside in the parts of the termites' gut that get shed when they molt, adds Oboyski. “That means every time that they molt, they lose their ability to digest wood. So they have to do a fecal transfer to get them back again. So they will feed on the feces of other termites to get those bacteria back.”
The Xerces blue (Glaucopsyche xerces), like the California Golden Bear, no longer exists. Endemic to the erstwhile dunes of San Francisco's Sunset District, the powder-blue gossamer-winged butterfly was presumably done in by urban development. Showing the Xerces at the Essig, Oboyski says, “It's rare to be able to document extinctions in the insect world, but this is one we're fairly certain about.” He calls this butterfly the “poster child of invertebrate extinction.” The Xerces blues were part of a family of little blue butterflies, some of which “have ridiculous relationships with ants. The ants actually take them into their colonies and feed them and take care of them.” It seems the caterpillars release pheromones that smell like the ants. The last known Xerces blue was netted by Berkeley alumnus and later UC Davis entomologist W. Harry Lange '33, in the Presidio on March 23, 1941. “I always thought there would be more,” he lamented later. “I was wrong.”