^^^^^^^^^^^^^^^^^^^^^^B

Transcription

1 o$a\j*\o^ \ wx trsoia....it is impossible to describe to Your Lordship what we have suffered here from the Musquetoes, and how much the work has been reduced, and I can take it upon me to say it [the finished survey map] would have been much better and higher finished had it not been for this inconvenience. Samuel Holland, 1/65 J\ s Islanders before and since ( \ Samuel Holland can attest, there are parts of the Island that rival the worst places in Canada for pest mosquitoes. In recent years ; they have even come to be seen as having an impact on the economy. In 1940 and again in 1952; an Ottawa insect specialist named Charles Twinn investigated reports of nuisance mosquitoes in and near Prince Edward Island National Park. He summarized the position of the innkeeper's association in his 1953 report: "Our beaches are outstanding and safe ; the temperature of the water ideal, we have some nice playgrounds, but on certain days no one can enjoy any of those facilities on account of the mosquitoes." Despite more than 50 years of control attempts, nuisance mosquitoes continue to be a problem, prompting frequent news reports about the negative impact of the mosquitoes on the tourism industry, especially in cottage developments and golf courses. Like it or not, they are a part of the Island way of life. What use are mosquitoes? Have they a place in the scheme of life besides making our lives a living hell when we try to enjoy the outdoors? There is no question that they are an important source of food for predators such as and bats. They feed primarily on plant nectar, so can also be important pollinators, especially in areas (like the Arctic) where bee pollinators are rare. But like other animals, the mosquito's primary goal is to reproduce itself, and that is the reason that most mosquitoes take blood. The blood provides much-needed proteins for the females to develop their eggs, which they can't get from their main diet of nectar. Consequently, only the females bite. When the female does bite, she first pierces the skin with her hypodermic-like proboscis, and injects a tiny amount of saliva containing an anticoagulant to keep the blood from clotting while she feeds. It is the anticoagulant that we react to when we get the characteristic bump of a mosquito bite. If the mosquito happens to be a disease carrier -< for example carrying the agent that causes malaria, yellow fever, several encephalitus diseases, among others - such organisms get passed on with the saliva, and can move into your bloodstream. Prince Edward Island has, at last count, 32 different species of mosquito. Biologically, mosquitoes belong to the family Culicidae - from the Latin for "gnat" - of the insect order Diptera, meaning "two wings," to distinguish them from most other insects that have four. The 32 species are sorted into seven genus subgroups. Probably the most important thing about all these subgroupings to us, as potential mosquito food, is that relatively few of the mosquito types are actually very pesky to humans. Of our 32 known species, only 22 are attracted to humans, and only five of these are common biters of people. But these few can form such clouds of misery that otherwise environmentally-conscious folks are driven to consider ways to murder them all off.

2 Life cycle... insects of various tribes were brought to life and maturity, as if by a miracle; the blood thirsty musquitoes sprung up in thousands and attacked the face, the hands and legs. If these are only covered with stockings, they manifest neither fear nor shame in prosecuting their designs of sucking the blood and instilling their poison. Walter Johnstone, A Series of Letter s D e s c r i p t i v e of P r i n c e Edward Island, 1822 Because I work at the University of Prince Edward Island; and have carried out some work on Island mosquitoes, I often get calls from the public asking how to deal with their mosquito problem. One major thing that comes u p time and time again is the lack of knowledge about mosquito b r e e d i n g habits ; with m a n y people believing t h at they b r e e d in the grass ; under porches ; and in the forest. This isn't a n e w idea... many early settlers believed that the mosquitoes bred in the forest, since w h e n t h e forest w a s cleared, t h e mosquitoes declined. Doug Sobey summarized this impression in his "Early Descriptions of t h e Forests of Prince Edward Island." In on e report, the cattle were "driven out of t h e woods by t h e flies 7 ' a n d in another, a settler "...cleared the coast on either side of w h a t is n o w the Brudenell Point for about three-quarters of a league... in order to make a passageway for m e n and animals, as well as to destroy mosquitoes." The notion that the mosquitoes bred in the woods was prevalent enough that the Island's House of Assembly passed a law in 1773 that allowed landowners to set fires in spring to burn the supposed breeding and harbouring sites. Other landowners saw a connection between mosquitoes and saltmarshes, as well as the woods, reflecting the fact that some of our peskiest mosquitoes breed in saltmarshes. In reality, all mosquitoes breed in standing water, and the connection between them and the woods is Pupa / chrysalide i4^ Eggs / oeufs Larva (4 stages) / larve (4 stades) Life cycle / Cycle biologique. simply the amount of standing water in t h e woods. Presumably, w h e n forest was cleared for agriculture, these standing water sites were also removed, a n d t h e mosquito problem also declined. The lands became more open to the breezes, which also helped keep the mosquitoes down. It is tempting, though, to suppose that ^^^^^^^^^^^^^^^^^^^^^^B 5*. iiii^yhl^iliiilii^h fertwj ' :- '' /m^j'n] II I l ^ i ^ p i l jjj 1(p^^^^^^^^^^^^B Ppl "The water temperature is just right for ocean swimming. The sand is soft and warm underfoot and the sun lingers long past the barbeque hour." Province of Prince Edward Island Visitors Guide, C1975. The salt marshes behind the sand dunes are also just right for hatching mosquitoes. «La temperature de Veau est ideale pour nager en mer. Le sable est doux et chaud sous les pieds, et le soleil disparait longtemps apres Vheure du barbecue.» Guide de Tile, province de Flle-du-Prince-Edouard, v Les marais sales derriere les dunes sableuses sont egalement propices a Yeclosion des larves de moustiques.

3 at least part of the land clearing habits here might have been due to the depradations of mosquitoes. The life cycle of the m o s q u i t o begins with a blood-fed and mated female, who lays her eggs on or near the water. The variety of mosquitoes also gives us a variety of life-cycle types. Some of our mosquito species have hardy drought- and cold-resistant eggs that get laid along the margins of forest pools, or in depressions that will fill with water w h e n the snow melts in spring. Others lay their eggs directly on the surface of the water in small floating rafts. These overwinter in small animal burrows (and more recently in barns or basements) as mated females ready to lay their eggs in the spring. They can be fooled by a warm spell in winter and prompt reports of mosquitoes flying in January or February. Two of our species overwinter as immature larvae one in the mud of marshes with emergent vegetation, and another in the frozen fluid inside pitcher plants. A few species produce only one generation in a year, usually in early spring, and others can go through multiple cycles, depending on the Coquillettidia perturbans Ochlerotatus abserratus opportunistic Ochlerotatus punctor Ochlerotatus cantator Ochlerotatus sollicitans Ochlerotatus stirnulans "Restful little villages are scattered along Island highways and byways.." Province of Prince Edward Island Visitors Guide, C1970. The preferred resting habitat for several species is in the vegetation seen at the edge of this pond. «A Vinterieur du reseau de routes pavees, on trouve des chemins bordant la mer et des routes panoramiques...» Guide de Tile, province de Flle-du-PrinceEdouard, v Les moustiques de Vile preferent les fosses. Plus de la moitie des especes trouvees id sen serventpour Yeclosion de leurs larves. water and air temperature, and the length of the season. Hatching can start almost as soon as the snow starts to melt in the spring, but the newly-hatched larvae grow slowly in low temperatures and may take as much as a month to go Preferred Habitat ponds with emergent vegetation sphagnum pool, cattail ditches and marshes, pond edges, mossy pools sphagnum pool, cattail ditches and marshes, pond edges, mossy pools mainly salt marsh pools, some fresh marshes (salinity range: o - 29%) ditch, salt marshes (salinity range: o - 29%) cattail & shrub marshes, ditches with rushes and alders, puddles, pond edges C o m m o n (6 to 10% of mosquitos collected) Aedes. cinereus Culex pipiens Ochlerotatus canadensis sts? **$? j^m? Preferred Habitat roadside pools and ditches, mud puddles, pasture pools, bog pools roadside ditches, water-filled tubs road ruts, mud puddles, pasture pools, bog pools, ditches, freshwater marsh from egg to adult. With the warmth of summer the cycle speeds up, and the process can take just a few days. The worm-like larva spends its entire time in the water, w h e r e it feeds by filtering bacteria, protozoa or small particles of organic material through a set of fine brushes located around its mouth. The larva usually hangs upside down from the surface of the water, b r e a t h i n g t h r o u g h a snorkel-like tube at the end of its abdomen - in other words, mosquitoes b r e a t h e t h r o u g h their b u m s! An early form of mosquito control was to pour oil or kerosene onto the surface of standin g water; the oil would clog the breathing tube, and the mosquitoes would drown. This was pretty drastic for other mars h plants and animals, though, and is not recommended today. Mosquito larvae can swim in a limited fashion, and their characteristic swimming motion has given rise to the common name "wrigglers" for this stage. Their b r e a t h i n g tubes only w o r k when the water is quite still, so they are restricted to shallow protected pools, or pools with lots of vegetation to prevent wave action from the wind. After four larval moults, they moult to a further stage called a pupa. The larvae are about one millimetre long when they first hatch, and reach up to five millimetres by the time they are ready to moult. The pupal stage in insects is one where a major metamorphosis occurs,

4 changing from a worm-like larva to a flying adult. This is a dynamic time, since many of the larval tissues are reabsorbed into the body Wings and legs are grown inside the pupal case, which looks a bit like a comma when you look at it from the side, hanging from the water surface. When the metamorphosis is complete, the pupa rises to the surface and splits, and the adult mosquito climbs out. After a brief period to allow its wings to inflate and dry, the mosquito flies away. Both males and females get their energy for flight from plant nectar, but very soon after emergence, the female begins to look for a blood meal to provide protein for her developing eggs. Some mosquitoes prefer, some feed only on, and others will feed on nearly anything in sight. One group even specializes on reptiles and amphibians! A few mosquitoes, including the pitcher plant mosquito, don't take blood at all, and get enough protein as a larva to mature a batch of eggs. Some others will take a blood meal if opportunity arises, but can mature at least some eggs even without blood; this kind is common in the Arctic, where blood meals may be a bit scarce. Male mosquitoes are rarely seen by humans, since they hide in tall grasses and other places with high humidity, except when they're swarming to mate with the females. They swarm in places where the females are likely to come to lay eggs, and are attracted to them by the sound of their buzzing. Although the buzzing sounds the same to us for all mosquitoes, each species has a slightly different frequency, and it is that ensures the male finds the female of the right species to mate with. After mating, the female searches for a location to lay her eggs. Those of the species that overwinter as eggs lay the eggs in places that will fill up with snowmelt. The eggs can last several years, so if we get low snowmelt years, the eggs just pile up, waiting for a year when enough water accumulates for hatching. Those with multiple generations either look for standing water to drop their eggs onto, or lay their eggs in the grass around pools, so that a bit of rain will flood them. This waiting for a rain ensures that there will be water in the pool for long enough for the mosquito larvae to finish development. Salt marsh mosquitoes tend to follow the timing of the tides, since the highest tides of the month will flood the breeding pools. Therefore we usually see peaks of salt marsh mosquitoes a few days after the high tides of the full moon each month. Some mosquitoes prefer to breed in small standing water habitats, and are common in muddy puddles, rain Aedes vexans Culex restuans Culex territans reptiles Ochlerotatus communis Ochlerotatus excrucians Ochlerotatus fitchii Ochlerotatus implicatus Ochlerotatus pionips Ochlerotatus provocans Ochlerotatus. triseriatus Anopheles earlei Anopheles punctipennis Culiseta melanura Culiseta morsitans Ochlerotatus decticus Ochlerotatus diantaeus 1 Ochlerotatus hexodontus i Ochlerotatus intrudens Ochlerotatus mercurator Ochlerotatus rempeli Ochlerotatus riparius Ochlerotatus sticticus don't Wyeomyia smithii blood-feed barrels, and other small containers. My students and I once found a discarded potato chip bag in the woods that contained about 300 developing mosquito larvae, and larvae of these mosquitoes are also common in discarded tires. One common humanbiting species here seeks out small tree-holes where branches break off of the main trunk, and lays their eggs in there. road ruts, mud puddles, roadside ditches, rocky puddles, pool in culvert roadside ditches, water-filled tubs bog pools, roadside ditches, mud puddles rocky puddle, cattail swamp roadside ditches (with cattails or alders, may be muddy), pasture pools, bog pools cattail marshes & pools, pasture & bog brackish & fresh pools near salt marshes, murky fresh marshes, cattail marsh, ditch freshwater marsh roadside ditches (with cattails or alders), pond edges, freshwater marsh tree holes muddy roadside ditches, marshes marshes no larvae found roadside pond, bog pools, freshwater sphagnum (bog) pools ditch, pond edges, bog pools no larvae found, identification uncertain ditch with alders marsh in cow pasture mossy pool, roadside pond pasture pools no larvae found inside pitcher plants

5 The adult mosquitoes are very delicate; and need high humidity conditions to survive, so we don't usually see them out on warm dry days. At those times, both males and females will hide in tall grasses or brush; waiting for the humidity to increase enough to come out to search for food. This is one reason that so many are active in the evenings or mornings, or seem to rise out of grassy fields or forest margins when we walk in them. West Nile Virus...we fell in with an extensive swamp covered with a kind of spruce fir stunted in its growth, generally not more than 5 or 6 feet high... hard, rugged and so intertwined as to render the whole to appearance utterly impervious. I had never seen the like, 'tho I had explored many hundreds of miles in the wild and unfrequented forests of America... I was not baffled by this obstacle nor by the remonstrances of my companions who wished to return, added to the extreme heat of the weather, much greater than in England, and the incessant attacks of moschettoes and other troublesome flies, which was such that we could hardly stop for a drink of water - the least relaxation of our hands and handkerchiefs in brushing them away producing Swarms like a Swarm of Bees just broke loose from the hive and ready to devour us. Robert Gray to Lord Hugh Seymour-Conway 1793 Mosquitoes created quite a buzz across the country a few years ago; when a new mosquito-borne virus was discovered in New York, with the potential to spread into new areas. The virus was identified as West Nile Virus (named for the area in Uganda where it was first noticed), and it spread quickly away from the New York area, following the routes of migrating. The main *v:*v1 &*",$i ' mosquito carriers for West Nile Virus are Culex mosquitoes, which at the time had not been reported to occur here. Surveys conducted by our lab at UPEI showed that Culex did indeed occur on Prince Edward Island as well as in neighbouring provinces, so there was some concern that the disease could come to the Island. This is actually a disease of ; humans and other, especially horses, are "incidental hosts." The disease can't breed in, but can become infected. A carrier mosquito must feed on an infected bird, then the disease has to multiply in the mosquito's blood and migrate to the salivary glands of the mosquito. This takes about 10 days, after which the mosquito can pass on the disease to another bird when it feeds again. Other mosquitoes aren't all that good at picking up and passing the disease, so the amount of virus must be quite high in the for opportunistic feeders, those that feed on all sorts of animals, to pick it up and pass it on to. Unlike Ontario and Quebec, and points further west in Canada, our Culex species here are usually not very active or abundant when the migrating pass through in the spring. This is mainly a function of temperature - our temperatures in April and May are still very cool relative to central Canada. This means that there is very little chance that the virus can enter our ecosystem in the spring, and the pass through without passing on the disease. Consequently, although West Nile Virus continues to be a problem in central and western Canada, it has not become a problem on Prince Edward Island. Controlling Mosquitoes On dull days the mosquitoes and sand flies were almost unendurable. My brother Johnny and I went one day to cut some hay My mother had ''Three special drives have been laid out... A few short sections are red packed put us up lunch in a nice pillowslip. clay which will add to the variety of your drive!7 Province of Prince Edward The flies were so vicious we could not Island Visitors Guide, C1975. Several of the Island's most common mosquito endure them; but we did not want to species lay their eggs in water-filled ruts on dirt roads like this. go home until we had finished our «Trois routes speciales ont ete congues... Quelques courts segments d'argile bien work. At last we got desperate and cut holes in the pillowslip and made tassee ajouteront a la variete de votre promenade.» Guide de Tile, province de a mask of it. We took turns wearing l'lle-du-prince-edouard, v Plusieurs des especes les plus communes de moustiques de Vile pondent leurs oeufs dans des ornieres remplies d'eau sur des this; it was good protection. When we got home mother discovered what we chemins forestiers comme celui-ci. had done to her nice pillowslip. But

6 time and m o n e y can be spent on programs that simply don't work. Another problem with mosquito control efforts is that mosquitoes can fly or be blown in from many kilometers away, so effective control can only be achieved with an extensive program finding and targeting all the potential breeding habitats active ingredient N,N-diethyl-m-toluamide, usually abbreviated to "DEET," are effective. Sometimes the advertisement is true - other repellents may give some protection, but not as much as DEET. Previous generawe have already heard of early tions that tended to leave only face efforts to control m o s q u i t o e s by and hands exposed in the summerburning or clearing forests. W h e n it time didn't seem to suffer as much, became clear that mosquitoes bred but modern "bug shirts" or in s t a n d i n g water, control " b ^ h a t s " give t h e same efforts focussed on "source sort of relief while working reduction/' a fancy name for HI or playing outdoors. If you draining wetlands. This was live near a mosquito source, particularly effective in conconsider a screened porch trolling mosquitoes breeding or gazebo for relaxing in in fresh and salt m a r s h e s, during the summer months. but didn't do much for the You can also keep the grass w o o d l a n d mosquitoes, and m o w n near your house to had negative effects for other! keep down the areas where wetland animals. By the end JiBBllWSHi the adults rest w h e n condiof t h e Second World War, y -. - '. " " ' -,- \: " the use of insecticides was "There are now seven excellent golf courses on the Island" tions aren't good for them b e c o m i n g m o r e prevalent, Province of Prince Edward Island Visitors Guide, C1970. to be flying. a n d DDT was p a r t i c u l a r l y Water hazards and nearby woods also make excellent Mosquitoes are insects effective at reducing mosqui- mosquito habitat. that we love to hate, and toes. Dr. Ed MacDonald at that relationship has a UPEI remembers DDT being «Vile possede maintenant sept excellents golfs.» Guide de long history here on Prince sprayed in PEI National Park File, province de l'lle-du-prince-edouard, Les fosses Edward Island. One thing to keep the mosquitoes down d'eau et les bois environnants fournissent egalement un is for sure, the mosquitoes for the campers, incidentally excellent habitat aux moustiques.» will still be here long after getting quite a lot of spray on Man has come and gone. over several square kilometres. In the campers as well. But DDT wasn't most cases, this is considered to be effective for long, since the rapidtoo expensive. ly-breeding mosquitoes developed Sources: Concerns for the e n v i r o n m e n t resistance pretty quickly. This led to c o n t i n u e to p r o m p t searches for a search for stronger and stronger Two useful scientific sources are: T.G. alternate methods for dealing with chemicals to keep the biting insects Floore's, "Mosquito Larval Control nuisanc e mosquitoes. A favourite under control, changing chemicals Practices: Past and Present/ 7 (Journal method is erecting bat boxes. This regularly as resistance developed. of the American Mosquito Control is great for our bat populations, but It is rare now to spray insecticides Association, 22, 2006) and D.J. Giber son, doesn't have much effect on the mosfor adult mosquitoes, because of K. Dau-Schmidt, and M. Dobrin's (2007) quitoes. Although bats can conceivadverse effects on other organisms "Mosquito species composition, phenolably eat thousands of mosquitoes in in the environment. Therefore, curogy and distribution (Diptera: Culicidae) a day, studies have shown that even rent efforts focus on the larval stage, on Prince Edward Island" (Journal of the in areas of very high mosquito numand mosquito control programs Acadian Entomological Society, 3, 2007). bers, they make up less than 20% of involve a combination of seeking Historical sources include: Doug Sobeys a bat's diet. Bats prefer larger insects, out and treating mosquito breeding Early Descriptions of the Forests of Prince such as m o t h s, w h i c h give t h e m sites. Currently, breeding sites are Edward Island: A Source-Book. Part I: m o r e p r o t e i n for less w o r k t h a n treated with a bacterial insecticide, The French Period ( ); and Part chasing mosquitoes. There has also Bacillus thuringiensis var. israelensis, II, The British and Post-Confederation been a proliferation of propane-powthat is highly specific to mosquitoes Periods ( ), (P.E.I. Department of ered mosquito attractors, in hopes of and their close relatives in the insect Agriculture and Forestry, Charlottetown, trapping out the populations of mosworld. This product consists of bac2002 and 2006.) The quote from quitoes before they can reach people terial spores that cause a fatal stomsamuel Holland is from his "Letters and to bite them. These have mixed sucach disease in the mosquitoes. The Correspondence," available at the Public cess; they do capture a pile of moscontrol is only as good as the success Archives and Records Office. The quote quitoes, but they also attract them in finding the breeding sites, though, from Robert Grey is from Doug Sobeys from much further away than if the and many sites with high numbers "A Journey Across Lot 13 in 1793/ {The traps were not there, while also libof mosquitoes are small and easily Island Magazine, #42, 1997). Special erating huge amounts of C0 2 to the missed. For example, control prothanks to Doug Sobey, Boyde Beck, and atmosphere! Few things work as well grams that focus on salt marshes Ed MacDonald, who provided the historias personal protection. Good repelwill miss the woodland and emercal references, y^*" lents, especially those containing the gent-marsh species, so considerable she could see from our swollen faces that we had suffered greatly. Henry Mellish, Timothy's Boyhood, 1934 iiiil 4 :>%.:-4fp