Between black flies, mosquitoes and ticks, spring and summer in Maine can be the season of the itch.

While black flies are a May-July seasonal nuisance in Maine, black flies don’t spread disease. Mosquitoes and ticks can, and do, including West Nile virus spread by ’skeeters and Lyme disease spread by deer ticks.

Charlene Donahue, an entomologist (translation: bug expert) with the Maine Forest Service, said this year’s mild winter didn’t kill off ticks in any significant way and that a relatively dry spring has only delayed the inevitable emergence of mosquitoes and black flies, which are water-dependent in terms of their numbers.

There are some 40 species of black flies in Maine, most with a lifespan of only a few weeks. The black fly larvae found in fast-flowing rivers and streams are an important food source for trout, salmon and other aquatic predators. As tiny winged insects, swarms of black flies are ring-the-dinner-bell meals for bats and for birds. For humans, black flies remain both a blessing and a curse.

Male black flies are docile, feeding on the nectar of flowering plants and serving as an important source of pollination for Maine’s wild blueberry crop. Females are another story. She-flies are voracious vampires. They feast on blood to nurture and sustain the hundreds of eggs that each will later deposit along inland watersheds, as they have for 30 million years.

Female black flies don’t sting. They bite. They use four slashing teeth to carve a shallow well in the flesh of birds and large mammals, humans included. As blood seeps into the well, chemicals in the tiny she-devil’s saliva provide both an anesthetic that numbs the nerves and an anticoagulant that keeps the blood meal from clotting while being lapped up. Those same chemicals cause the resulting wound to swell and to itch once the instinctive, maternal feeding frenzy ritual is over. She’s gone, unswatted; you’re bleeding. Such is 30 million years of evolution.

Maine’s black flies are both cussed and discussed, the former by hikers and gardeners, the latter by the Machias-based Maine Blackfly Breeders Association (Motto: May the Swarm Be With You). A whimsical, nonprofit charitable organization, the association credits black flies with helping to keep people from away, well … away. Members delight in the notion of New Jersey tourists tending their black fly wounds while racing home on I-95, wondering aloud why anyone would live in a place like Down East Maine infested with the creatures.

The association’s membership is also fond of black fly-based limericks, including this one:

Maine black flies are small if there’s one,

But a swarm can darken the sun.

If you see it, don’t greet it,

Don’t stand there, just beat it.

Don’t look up, put your head down and run.

That may be spot-on advice, as black flies fly at one mile per hour.

Nothing funny about West Nile

While black flies may be the stuff of both tourist angst and people-from-here whimsy, there’s nothing funny about West Nile virus, which is spread to animals and humans by infected mosquitoes.

Last year, the federal Centers for Disease Control and Prevention reported 5,387 cases of West Nile virus in people within the continental United States, including 234 deaths. Half of those infected contracted neuroinvasive diseases, including meningitis and encephalitis. Since 1999, when the virus first emerged in New York, 30,000 people have been infected.

Until last year, Maine had dodged the West Nile bullet. Although the virus was previously detected in birds and horses in Maine, there wasn’t a confirmed human case until last fall, the last of 48 states to document human West Nile infection. Hawaii and Alaska are, so far, unaffected.

In October 2012, a 34-year-old Cumberland County man was diagnosed with complications of West Nile — fever, weakness, double vision and brain and spinal cord swelling. He was hospitalized and survived.

The Maine Center for Disease Control and Prevention notes that most people infected with West Nile virus have no obvious symptoms. In those who do, symptoms include headache, high fever, altered mental state, tremors, convulsions and, rarely, paralysis, meningitis and encephalitis. The agency also notes that there is no specific treatment for West Nile virus, which can be fatal.

Ticks and Lyme disease

While seldom fatal, Lyme disease is a public health scourge for Maine and other Northeastern states, causing debilitating symptoms that can last a lifetime. Beyond New England, Lyme disease is also a problem in Wisconsin and Minnesota, which are also heavily wooded and highly populated with deer.

Lyme disease is transmitted to humans through the bite of infected black-legged ticks, which are common deer parasites eager to attach themselves to deer and to those hiking through deer habitat. Typical human symptoms include fever, headache, fatigue, and a signature “bulls-eye” skin rash. If left untreated, the bacterial infection can spread to joints, the heart and to the nervous system. Most cases of Lyme disease can be treated successfully with antibiotics.

The incidence of Lyme disease has increased dramatically in Maine over the last 20 years, with a record-high 1,100 residents diagnosed last year. Federal CDC numbers show that, since 1992, the incidence of Lyme disease has increased to 76 per 100,000 residents, with children between the ages of 5 and 14 the most susceptible, at 111 per 100,000.

Maine CDC notes that Lyme disease triggers skin, joint, nerve and heart problems. Those infected with Lyme disease are typically the host to an infected, parasitic deer tick that attaches to their bodies for 24 to 48 hours. Untreated Lyme disease can lead to skeletal, cardiac and nervous system disorders.

While seldom viewed as more than a vacation-time nuisance easily dispatched with of burst of “Off,” these tiny human predators can be killers. Humans beware.