- Kim Scafuro
We depend on 1,000-pound cows for milk and meat, and snuggle up with our 40-pound dogs and eight-pound cats. But an inversely proportional relationship governs the ways in which our lives are shaped by the creatures around us: The smallest animals can have the greatest impact. Just ask your friendly neighborhood pathologist. The bacteria and viruses that truly rule the world exist outside the animal kingdom — and hence outside the purview of this issue. But, way bigger than bacteria, unbelievably numerous and generally more reviled than celebrated, insects of all kinds affect us in complex and fascinating ways.
Vermont has a rich entomological culture, even if most of it exists on a scale that we don't often consider. The state's insects are beautiful (the Canadian tiger swallowtail butterfly, Papilio canadensis); irritating (ants on your kitchen counters); potential disease vectors (the Anopheles mosquito); and essential to our economy and very survival (pollinating bees).
In Bug World, something interesting is always going on. Here are some current dispatches from the state officials and researchers who keep their eyes trained on Vermont's insects — and one indomitable little arachnid.
According to a 2008 survey prepared by state entomologist Alan Graham, Vermont is home to at least 45 species of mosquitoes. If that sounds like a lot, consider that more than 3,000 mosquito species exist worldwide. Vermont's mosquito problem could be much worse.
Still, the insect's population here could represent more than just summertime botheration. Some of them are carriers of the Eastern equine encephalitis (EEE) virus, which causes a rare but potentially fatal disease not only in horses but in humans. Two Vermonters died from it a couple of years ago, perhaps after having contracted the virus from mosquitoes.
Graham, in a phone conversation with Seven Days, says the state has been monitoring the mosquito population for disease since 2001. At that time, the primary area of research was West Nile virus; now, with the threat posed by "triple E," the Agency of Agriculture is stepping up its efforts.
"We are concerned," says Graham, citing reports of EEE cases in New Hampshire, Québec and Clinton County, N.Y., just across Lake Champlain. "We have tried to intensify our trapping to look specifically for this virus, in addition to West Nile virus," he says.
In 2011, several emus in Addison County died from EEE. Native to Australia, these giant birds had no resistance to the virus; Graham likens them to the proverbial canaries in a coal mine. The ag agency decided to ramp up its mosquito study partly in response to those emu deaths.
Another recent study, conducted in collaboration with the Connecticut Agricultural Experiment Station, revealed that many mosquitoes pick up the EEE virus from feeding on passerine birds, a large group that includes many songbirds. But about 6 percent of those mosquitoes' diets came from mammals, meaning there's a risk of the bugs passing EEE along to human hosts.
At present, Graham acknowledges that we can't do much beyond applying insect repellent. The risk of contracting EEE is low, but not zero.
Though it's not exactly breaking news, the latest on ticks is hardly more uplifting. Put simply, Graham says, "There's been a large increase in Lyme disease and a large increase in deer ticks in pretty much all regions of Vermont."
What makes this incidence so remarkable is that the deer tick, the primary vector for Lyme, could not be found in Vermont as recently as 40 years ago. The insect's northward march has been incredible. According to Graham, the quarter-inch-long deer tick is traversing about 50 miles, or roughly 12.6 million times its body length, every year. In human terms, that's the approximate equivalent of traveling from Paris to Vladivostok annually.
Many people consider ticks (which are not insects but arachnids, related to spiders) to be icky, blood-sucking things, but that's not the worst of it. The northbound trek of the deer tick has put Vermonters at a greater risk for Lyme disease. The first step in mitigating Lyme is to understand all we can about its primary vector, says Graham. But that's not so easy in a state with a small tax base, where such government-funded projects are less likely to attract funding.
Graham's agency has therefore teamed up with those of other states (he mentions Connecticut, Maine, New Hampshire and New York), as well as with the Centers for Disease Control and Prevention. Lyndon State College associate professor of biology Alan Giese has led a "quantitative surveillance" study of local tick populations, Graham adds. But he admits that a great deal more research must be completed before we can address the damage wrought by this diligent arachnid.
Honeybees and Bumblebees
Creatures such as mosquitoes and ticks make human lives more difficult, but from an insect's perspective, the human species is the most noisome nuisance. Not only do we go to a great deal of effort to eradicate certain insect species, we also kill off many others without even meaning to do so.
The most prominent example of accidental extirpation involves honeybees. In Vermont, as elsewhere, these vitally important insects have had some pretty tough years lately. Colony collapse disorder (CCD) has appeared in many headlines over the past decade, but, says Vermont state apiculturist Steve Parise, "We haven't documented any cases [of CCD] in Vermont."
That doesn't mean Vermont has not seen any CCD cases, which seem to stem from a complex system of interlocking problems including mite infestations, weather variations and viruses. Parise, who spends a lot of time inspecting beehives all over the state, has seen many in poor shape, but none that exhibited what he calls the "classic" symptom of CCD: A healthy hive suddenly and mysteriously losing the majority of its adult population.
Parise singles out recent changes in local agricultural practice as actions that adversely — although inadvertently — affect insects. More and more Vermont farmers, he says, are depriving bees of a major source of nectar in one of two ways. They're either clearing their hayfields before the constituent grasses have a chance to bloom or replacing hayfields with such crops as corn and soybeans, which, Parise notes, "promise little in the way of nectar resources for bees."
Wind, not bees, pollinates corn; soybeans produce little nectar. But these crops are valuable to farmers, either as feed for their livestock or on the open market. According to an online commodity calculator developed by the University of Illinois, the average price of a bushel of corn rose from $1.86 in 2000 to $6.15 in 2013. It's the very definition of a cash crop, yet its cultivation creates collateral insect damage.
Without hayfield crops such as clover, which holds its blooms for a long time and is a major source of nectar, bees don't get the nutrients they need to sustain their colonies or produce honey. When colonies are thus stressed, says Parise, they become more susceptible to "other factors that, by themselves, might not have been an issue," such as disease and infestation by the now-notorious varroa mite.
Such problems necessarily reduce the state's honey yield; then again, Parise says, they have also contributed to honey's current record-high prices. Recent weather has been favorable for honey making, but Parise isn't making any predictions. Speaking by phone to Seven Days in mid-June, he says, "The next eight weeks will tell the story for [this year's] honey production."
Another terror that humankind has visited on bees is the class of pesticides known as neonicotinoids (chemically related to nicotine). Often listed as one of the potential causes of CCD, neonicotinoids have the advantage of low toxicity for mammals. For insects, however, it's another story, as these chemicals attack their nervous systems and affect, among other things, their ability to navigate.
Kent McFarland is a conservation biologist with the Vermont Center for Ecostudies in Norwich. He's led a multiyear project that yielded an alarming result: Nearly a quarter of Vermont's native bumblebee species has disappeared in the last 20 years. Though he doesn't have the data to prove it yet, McFarland suspects neonicotinoids might be a root cause.
The biologists who conducted the study took a "bumblebee census" across the entire state of Vermont, collecting more than 10,000 specimens. Then they compared their data with those from the state's historical records back to 1900. Their conclusion, McFarland says, was "pretty alarming. Almost half of [Vermont's] bumblebee species are declining or appear to have declined. And three or four species have completely disappeared."
Historical records show only 17 total bumblebee species have ever resided in Vermont. With several previously common species, such as the rusty patched bumblebee, on the wane, the numbers do not look good for these important pollinators.
Any tomato grower will tell you that a decline in the bumblebee population is a serious matter. These insects vibrate their wings at about 400 Hz, which happens to be the frequency at which tomato plants' pollen is most easily dislodged from their anthers. "Buzz pollination" is so effective that producers of greenhouse tomatoes commonly set up bumblebee hives inside their facilities.
McFarland says he suspects that it's not just neonicotinoids that have been "whacking" these bees, but also the increased presence of Old World (that is, European) mites and gut parasites that encountered New World bumblebee species 30 years ago or more, before regulations were enacted to limit such contact. "Start adding these issues together and it spells big trouble for some of these bees," McFarland says.
Not all of McFarland's news is bad. He's recently been surveying the local population of the giant swallowtail butterfly, and his data suggest that this gargantuan, beautiful, harmless insect is on the rise in Vermont.
With a wingspan of up to six inches, the giant swallowtail is the single largest butterfly in North America. And, so far as McFarland can tell, it never appeared in Vermont until 2010. A number of sightings by "citizen scientists" (as McFarland calls amateur entomologists) was sufficient reason to commence a tracking program in the following year. "Now," he says, "it's breeding here all over the place."
In such southern states as Florida, the caterpillar form of the giant swallowtail can damage citrus crops. There's no such worry in Vermont, where it feeds primarily on a weedy, native plant called prickly ash, which has little commercial value.
What's driving the Papilio cresphontes north? It may be a gradual warming of the local climate ... so maybe it's true that most insect news is bad news. Insects — by virtue of their size, high reproduction rates and environmental sensitivity — tend to be biological bellwethers. All the more reason to heed what they're telling us.