Horsefly ready to bite an arm. Photograph captured from the Internet.
In which we examine the various summer insects that want to drink our blood
by Joe D. Shorthouse
MANITOULIN: Insects are the most abundant animals on Manitoulin Island. There are more types of insects here than all other types of animals combined and our natural ecosystems would collapse without them.
Most Manitoulin insect species are not even noticed, as they spend their lives providing ecosystem services, such as decomposing organic matter, eating other insects, or pollinating plants.
However, some types cause us endless pain because they feed on our blood. These insects, and some other types of small animals that also feed on blood, are the subject of this two-part series.
Part 1 discusses mosquitoes, black flies, horses, and deer. Centuries ago, they all fed on the blood of deer, elk, snowshoe hares, and birds, but once humans arrived, we quickly expanded their feasting options.
In Part II, lice, fleas, bed bugs, and ticks are discussed. Ticks are not insects, but because they are related arthropods of concern to Manitoulin Island residents, they are included.
While most of us cringe at the thought of animals eating our blood, a few hours at the exhibit gave a new perspective on the role blood feeders play in our environment and the surprising ways in which that adapt to their way of life.
For the animals discussed in these two articles, blood is an energy- and nutrient-rich food source used to produce eggs. However, a problem for all vertebrate blood feeders is that blood easily clogs the small mouthparts. To avoid this, blood feeders have developed anticoagulants in their saliva.
Although anticoagulants solve a problem for blood feeders, it is saliva that is responsible for much of our discomfort when feeding and, in many cases, it is saliva that spreads disease.
There are two types of blood feeders: so-called capillary feeders and pool feeders. Capillary feeders such as mosquitoes, bedbugs, lice and ticks have mouthparts modified to form two flexible tubes in which they seek a blood meal from a vein beneath the surface of the skin.
Anticoagulants are injected into one tube to prevent the blood from clotting, while blood is suctioned into the other. They can usually feed without alerting the host to their presence.
Pool feeders such as horse flies, deer flies and black flies cut a hole in the skin and wait for blood to flow freely and pool. They add anticoagulants to the drop and lick the blood that collects on the surface. The bite of most pool feeders is painful.
mosquitoes
Adult mosquitoes are the flying insect that people dislike the most. They buzz in our ears while we try to sleep, and their bites leave us itchy, sore and swollen.
There are about 82 species of mosquitoes in Canada, 67 in Ontario and probably about 50 species on Manitoulin Island. The appearance of the adults of each species is dispersed throughout the season so there are mosquitoes that bother us throughout the warm months.
Although they are delicate little flies, mosquitoes are the deadliest animal to humans on the planet because of the infectious diseases they transmit. Mosquitoes kill hundreds of thousands more people in the world each year than all other deadly animals combined.
Mosquitoes are both aquatic and terrestrial; however, they spend most of their lives in the aquatic stage. Eggs are laid in stagnant water and hatch into mobile larvae called wrigglers that feed on microscopic algae and detritus floating in the water.
Larvae cannot breathe underwater and must come to the surface where they use a breathing tube on their dorsal surface to obtain oxygen. The larval stage lasts from six days to two weeks depending on the species and water temperature.
Unlike most other insects, the pupal stage of mosquitoes actively swims, but does not eat. It has a coma-shaped body and also has to come to the surface to get oxygen.
Although mosquitoes are delicate, they can fly long distances and have an uncanny ability to locate human hosts. Adults are about 6-8mm long, with long webbed legs.
Their heads have large eyes and a pair of long antennae. The antennae of the males are bushier than those of the females and contain auditory receptors to detect the characteristic whine of the females’ wings. Mosquito wings beat 300 to 600 times per second.
Their large eyes allow them to see people several meters away and feel on their antennae to detect the levels of CO2 and other compounds expelled as we breathe.
They can detect sweat and other body odors, along with body heat, and as a result some people are more attractive than others. Mosquitoes can smell body odor and CO2 up to 20 meters away.
Adult mosquitoes can feed at any time of the day, depending on the species. Most species feed actively at dusk or dawn. Both females and males feed on nectar which they use as energy; however, only females feed on blood which is used to produce eggs.
Most mosquitoes feed on warm-blooded mammals or birds. West Nile virus is transmitted by mosquitoes that feed on birds.
Development from egg to adult takes about 40 days. Adults live one to two weeks. Most mosquitoes rest in a cool place during the heat of the day and wait until the evenings before looking for food, although they may still bite if disturbed.
Mosquitoes are some of the most adaptable and successful insects on Earth and they are found in some extraordinary places. Virtually any natural or artificial water collection can support mosquito larvae.
Mosquitoes have been discovered in mines nearly a kilometer below the surface and on mountaintops 420 metres. Mosquitoes easily fly through the open windows of vehicles and homes and look for human inhabitants to feed on.
black flies
Black flies are small, robust (mostly 5 to 8 mm long), black or gray flies that are a scourge on people and livestock across Canada. They are more common from mid-May and can continue to make us miserable until June or even July. They may bite at any time during the day, but do not feed at night. Unlike mosquitoes, they are not delicate and are shaped more like a small prairie buffalo, hence their other common name “buffalo mosquitoes”.
Black flies have a habit of swarming and are most annoying when they get under our clothes and feed on our blood without us noticing. They do not spread disease among humans, although their bites are painful, itchy and slow to heal. Some people have an allergic reaction to their bites.
Black flies have short legs and antennae. There are 162 species in Canada and about 63 in Ontario and at least 40 on Manitoulin Island.
Like mosquitoes, they are both aquatic and terrestrial and most of their life is spent as larvae in the fresh waters of streams and rivers.
They have one generation per year. Their eggs are laid on the banks of streams and rivers in mid-summer. When the larvae hatch, they sink to the bottom where they attach to rocks using hooks at the rear end.
The larvae are shaped like small urns and bend in the direction of the current with the head downstream. Their mouthparts consist of folding fans that expand when feeding to trap passing debris such as organic particles, algae, and bacteria. Larval scratches captured food in their mouths every few seconds.
Larvae turn into pupae, an inactive stage of development during which they do not feed. The pupae develop into adults that float to the surface in an air bubble.
Adults are ready to fly when they emerge from the water and immediately seek a blood meal. They may lay eggs shortly after a blood meal. The average lifespan of an adult black fly is three weeks.
Mature adults can disperse tens or hundreds of kilometers from their breeding sites under their own power or aided by prevailing winds, complicating control efforts.
Both males and females depend on plant nectar for their flight energy, while females need blood for egg development. Males are rarely seen and do not feed on blood.
Females have specialized mouths with serrated “stilettos” that they use to cut through the skin to reveal blood vessels. Anticoagulants in saliva also partially numb the feeding site, reducing the host’s awareness of being bitten and thus prolonging the flies’ feeding time.
Blood continues to pool at their feeding sites after the flies have left. Feeding often causes localized swelling and inflammation and the site becomes itchy. Heavy feeding can cause “black fly fever,” probably caused by the anticoagulant, causing headache, nausea, fever, swollen lymph nodes, and joint pain.
Black flies feed only during daylight hours and tend to concentrate on areas of thinner skin such as the nape of the neck or ears and ankles. Of interest, they will not feed on humans inside vehicles or houses. Black flies on Manitoulin Island do not transmit disease.
Horse flies and deer flies
Horse and deer flies are large, robust flies with prominent compound eyes. As their names suggest, their main food sources are the blood of large animals such as horses and deer. However, they will feed on any large mammals they can find such as cows, dogs and humans.
Deer flies will readily seek human blood, while horse flies feed less frequently on people. Both flies are often found buzzing around stables and fields. Depending on the species, we can be bothered by thrips and deer flies from May to September.
There are about 3,700 species of horseflies in the world and 144 are found in Canada. There are about 44 species of deer flies found in Canada, most likely found on Manitoulin Island.
Horses and deer flies can be…