We left Cedar Key, Florida in late April when it was warming up and the sand gnats were coming out in force. Also called no-see-ums, the sand gnats would swarm around early and late in the day, especially when it was calm. They have small scalpels for biting mouthparts, inject a bit of anti-coagulant and drink your blood. I've become a bit used to them but I still get welts that itch for a day or two. Once in Belize my legs looked like they took a hit from a shotgun with sand gnat bites all over.
John Lewinski of McCall, Idaho; Ken Schreiber of Osseo, Wis.; Dennis Anderson of River Falls and I have been going on week-long June fishing trips for over 20 years. For the sixth year in a row we rented a nice house for a week on Big Round Lake in Polk County. Dennis and I brought our fishing boats. The late spring had delayed bluegill spawning. Despite fairly clear water, we couldn't see bluegill spawning nests on the gravel bottom areas where we had found them in past years. Fishing was slow but we caught plenty of good-sized bluegills, many over 9 inches long.
In past years we were plagued by mosquitoes when we returned to the house to clean fish. This year mosquitoes were scarce and squadrons of dragonflies kept them at bay.
When I returned home last Saturday, our place was thick with gnats. My wife Carol was wearing a hat with a head net when working in the garden. It's hard to ignore the swarm of small insects buzzing around your head when outside these days. Not only do they aggravate but some of them bite. They seem to focus on ears and the zone just beneath hat bands. I think they are worse than mosquitoes.
The pesky buggers are Dipterans of the family Simuliidae; two-winged tiny insects called biting gnats, buffalo gnats, black flies and many other unprintable names. There are about 30 species of them in this region. Some don't feed on humans and just buzz around. Others have slashing mouthparts and draw blood to obtain nutrients to help them produce eggs. The biting flies inject an anticoagulant into the wound which makes for painful, itchy bites.
Gnats can kill chickens by clogging their nostrils. My brother-in-law Ken Schreiber said that his chickens don't want to leave the coop when gnats are dense. He puts covers over their horses' heads to keep the gnats from biting them. Farther north where black flies are really abundant, they can drive people crazy and force black bears to dive into the water.
Black fly larvae live in cool or cold well-oxygenated streams. The larvae attach to wood or rock and filter out fine particulate matter to eat. They live as larvae for about a month, enter a pupal stage for a few days, and then float to the surface to emerge as adults. The adults live for a few weeks, mate, and lay their eggs on or just above the water. Several generations can grow each summer. We've had near-record rain this spring, providing plenty of flowing water for the gnat larvae to grow in. I've been surprised to find swarms of gnats on hilltops far from flowing water but they are especially abundant near streams and rivers. Fortunately, biting gnats don't transmit pathogens like mosquitoes but scratching bites can cause infections.
Around the Twin Cities, the mosquito control people treat streams with the natural product, Bacillus thuringiensis var. israeliensis (Bti) to kill black fly larvae but the high flows this year have rendered that ineffective. We may have fewer gnats around our place due to the squadrons of dragonflies and bats flying around dining on them in the evening.
I've found that insect repellents with plant-based oils like geraniol, citronella and vanilla are pretty effective against gnats. Insect repellants with DEET seem to attract them but do fend off mosquitoes and ticks.
When fishing on the Kinnickinnic and Rush rivers recently I've learned to live with the swarm of gnats buzzing around my head and appreciate the fact that the trout and other fish are feeding on their larvae.
A spell of dry weather should reduce the abundance of gnats. I hope they are gone before they get all my blood.
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