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Mosquitoes
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family: culicidae
Wear baggy, long-sleeved shirts and pants.
It doesn’t take much time, or water, for mosquitoes to develop from eggs into adults. Therefore, any thing that can hold water is a potential development site. To destroy common mosquito breeding sites around your home, consistent yard maintenance is the best defense. We can all reduce risk by doing the following:
If there is a large area of stagnant water near your house, but not on your property, that you are concerned about, please contact your local engineering or public works department. Arrangements may be made to drain it or prevent mosquitoes from breeding in it.
(Please note that, under provincial regulations, pesticide treatment of any bodies of water other than those that are human-made and self-contained on private land can proceed only under permit or similar provincial authorization.)
Mosquitoes About 60 species of mosquitoes occur in Canada, and because females require a blood meal to develop eggs, they are a serious pest of humans, livestock and wildlife during spring and summer.
Mosquitoes cause much annoyance and discomfort to humans and animals. Their attacks reduce beef and milk production, and lessen the efficiency of agricultural, forestry and other workers, They also interfere with recreation and spread diseases.
Mosquitoes
develop only in stagnant water, and pass through four distinct
life stages — egg, larva, pupa and adult. A female may
lay over a hundred eggs these are deposited either singly on the
soil among grass roots and organic matter in low places where water
collects, or in rafts on the surface of Most common mosquitoes (Aedes spp.) pass the winter as eggs that hatch when flooded with water. The less common mosquitoes (Culex spp., Culiseta spp. and Anopheles spp.) pass the winter as fertilized females in cellars, animal burrows, hollow trees, basements and unheated buildings; they appear early in the spring and the eggs of these species hatch shortly after they are laid.
Mosquito control is difficult because of the diverse habits and breeding places of the different species, Consult your provincial Departments of Health, Environment and Agriculture for control procedures recommended for your area. last updated on the 16th of September 1995 by G.J.L.Ramel@exeter.ac.uk Mosquitoes (Culicidae, suborder Culicinae) 1,500+ species Worldwide, about 42 in the UK. These are the most important group of flies in this suborder. The word mosquito is Spanish and means 'little fly'. Mosquito adults can be recognized because they are the only family of flies which have both the veins of their wings covered in scales (very rare in any flies at all) and a long projecting proboscis. Flies in general are lovers of the light but not mosquitoes most of whom are true denizens of the night. Not all species of mosquitoes are blood suckers and in those species which are it is only the females which do; this is because they need the protein to develop their eggs. One genus of mosquitoes called Harpagomyia have learned how to rob ants of the genus Crematogaster. The mosquito alights in front of an ant returning to its nest beating its wings whereupon the ant opens its jaws allowing the mosquito to use it proboscis to remove the contents of the ants crop. Mosquitoes have aquatic larva and one species or another lays its eggs in most areas of still water from large lakes to puddles and knot holes in trees. Two very interesting groups are the genus Trypteroides which lays its eggs in the urns of the Pitcher plants of Indo-Malaya and Australia despite these being filled with digestive enzymes used by the plant to consume the insects trapped within and the genus Megarhinus whose larva are carnivorous and live in the same pitcher urns feeding on the larval Trypteroides. The strangest place any fly lays its eggs is on its own legs, this is done by the mosquitoes of the genus Amigeres the females carefully places each of her eggs onto her legs where they diapause (a kind of hibernation) until the female immerses her legs in water, the stimulus of the water causes the eggs to fall off their mothers legs and to come out of diapause so that they can hatch in the water in the normal way.
Abstract The mosquito Culex
pipiens form molestus is easy to rear because
the adults do not need a blood meal. This paper describes methods
for maintaining a stock culture and for producing cohorts
Mosquitoes, Culex, rearing, surface film, predators, control.
Mosquitoes are important vectors of disease, especially in the tropics. Resistance to conventional insecticides is a serious and growing problem (Brookfield, 1991), and increasingly attention is being paid to alternative methods of control. Among the weapons available for use against the aquatic stages of mosquitoes are oils and insoluble surfactants such as Arosurf 'Monomolecular Surface Film', insect juvenile hormone analogues such as methoprene, and natural enemies that can be introduced as biological control agents (Laird & Miles, 1985). Microbial control agents include bacteria such as Bacillus thuringiensis israelensis, which is commercially available for application to mosquito larval habitats, and the fungi Coelomomyces and Culicinomyces. Parasitic nematodes have also been suggested for biological control of mosquito larvae. Potentially useful predators include dragonfly larvae (Sebastian et al., 1990), the water boatman Notonecta, the magnificent predatory mosquito Toxorhynchites, and fishes such as the mosquito fish Gambusia affinis or the guppy Poecilia reticulata. Research is needed to discover how effective such methods may be in different conditions, and to explore the possible interactions between them. For example, if oils act by preventing mosquito larvae or pupae from gaining access to atmospheric air at the water surface, are these oils ineffectual in well-aerated water where the immature mosquitoes can get oxygen from solution in the water? If mosquito larvae in water butts in Trinidad are controlled with a film of an insoluble surfactant such as Arosurf 'Monomolecular Surface Film', might control be improved by adding a water boatman or a guppy to each container, or would these predators be harmed by the surfactant? If dragonfly larvae are introduced into domestic water cisterns in Myanmar (Burma) to control mosquito larvae, might control be improved by adding a guppy, or would the guppies and the dragonfly larvae eat each other? There are endless opportunities for potentially useful research on mosquitoes, using relatively simple equipment. The world's most notorious vector species do not occur naturally in Britain, and we do not recommend them as experimental subjects in schools and colleges, but useful work can be done on related species that occur in Britain or that can easily be reared in the laboratory. Snow (1990) describes the ecology and identification of British mosquito species and suggests approaches to field studies. A British species easily reared in the laboratory is Culex pipiens form molestus, and in this paper we outline a simple method for keeping it in culture. The London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT is usually willing to supply eggs for starting cultures. C. pipiens form molestus has several features that make it easy
to rear. First, whereas most other mosquitoes need a large space
in which to swarm and mate, this form can mate in a confined The methods we describe are not infallible. Rearing mosquitoes is as much an art as a science, and adjustments will have to be made to meet individual circumstances.
We keep a source culture ticking over with little attention through the year in three large containers. We use translucent 22.5-litre (40-pint) barrels designed for making home-made beer (Boots; 22.49 each in February 1993, complete with tap) (fig. 1) in a 27oC room (12 hr light: 12 hr dark). Each barrel is filled to about one-quarter to one-third of its depth with water. Cheaper and less robust alternatives are available, such as the Boots 25-litre winemaker's fermenting barrel, or a translucent polythene fermentation bin (15-litre bins cost 3.55) with a fitted lid from which an area can be cut away and replaced by a glued-on sleeve of netting. In either case, a tap (Boots barrel tap, 7.25) needs to be fitted in a hole drilled in the wall of the bin about 2.5 cm above the base. It can be sealed in with aquarium sealant. The beer barrel mouth is wide enough to admit a hand and arm for cleaning. There are two holes in the screw cap. The smaller hole (diameter about 0.5 cm) is exposed by unscrewing the pressure relief valve and the larger one (diameter about 1.5 cm) by unplugging the rubber stopper in the centre of the lid. Through the smaller hole we run a 0.5-cm-diameter air pipe, ending inside the barrel in an air stone (available from shops that sell aquarium accessories) which allows air from the air pump (Rena Aquarium Air Pump 301, @ 24.49 in October 1992) to bubble air into the water. If an aquarium air line plastic tap is introduced between the pump and the air stone, the flow of air can be regulated. It is usually best to adjust the bubbler so that there is only a gentle trickle of air. If the bubbles are fierce, they make it difficult for the larvae and pupae to break the water surface for gaseous exchange, they disturb adults that are emerging or standing on the surface to lay eggs there, and they capsize the egg rafts, breaking the eggs' contact with the water and preventing many of them from hatching. The larger hole in the cap is the right size to support a free-standing plastic funnel with a 15-cm-diameter mouth. A wad of cotton wool in the funnel prevents the escape of adult mosquitoes, and can be removed when water, food (in suspension or in solid form) or livestock is to be introduced into the barrel through the funnel. We also drilled a series of 30-50 holes, 0.2 cm in diameter, in the screw cap. These holes are small enough to prevent adult mosquitoes from escaping, but large enough to allow some ventilation of the barrel contents. They are restricted to the lid because this can be replaced cheaply if the barrel needs to be used for another purpose later. The Boots beer barrel has a tap at the bottom through which the aquatic component of the culture may be removed, without allowing the adults to escape. Larvae and pupae are easily drained out through the tap, but the egg rafts float on the water surface, and to withdraw these it is necessary to tilt the barrel, bringing the water surface level with the tap and allowing the surface, with its egg rafts, to dribble out. While the liquid from the barrel is run out into a washing-up bowl, the fate of the egg rafts can be monitored by looking through the peep hole ordinarily occupied by the funnel.
C. pipiens molestus larvae feed when hanging below the surface by filtering out small particles suspended in the water, or swim down to browse on the bottom of the container. There are several possible food sources. A mixture of desiccated liver powder (catalogue No. L. 26 from Unipath Ltd, Wade Road, Basingstoke, Hampshire, RG24 0PW at 13.01 for 250 gm), dried yeast (Yesta 20B at 44.25 per 25Kg from BFI-The tastemakers, Beesham Food Ingredients, P.O. Box 18, Wellington Road, Burton-on Trent, Staffordshire, DE14 2AB; or in small quantities from health food shops) and sugar, in the ratio of 3:10:2 by weight, at one level teaspoonful per barrel every 4-5 days, has sustained our colony for eight years. But the liver powder is expensive, and the soupy bacterial community that this food supports, and on which the mosquito larvae feed, is unpredictable and somearial foul-smelling. If the temperature is too high or there is too much food, undesirable anaerobic micro-organisms develop. If the soup becomes really foul, a stronger blast of air bubbles for an hour or so may help to drive out any noxious gases. Because of the unpredictability of the liver/yeast/sucrose diet and the cost of the liver, we have explored alternatives. One of our cultures has survived for six months solely on yeast and sugar, in the ratio of 5:1 by weight (one level teaspoonful per barrel at 4-5 day intervals), and is still flourishing. Some people feed mosquito cultures on Farex baby food. Perhaps the most convenient food is that recommended by the London School of Hygiene and Tropical Medicine: Guinea Pig Food (RGP pellets code 678, manufactured by Grain Harvesters Ltd., The Old Colliery, Wingham, Nr. Canterbury, Kent CT3 1LS, who will also supply on request a breakdown of the composition of the guinea pig food). This is available in small quantities from pet shops, or in much larger quantities from Wm. Lillico & Son, Wonham Mill, Betchworth, Surrey RH3 7AD, at 13.18 per 25-kg pack plus a surcharge for small orders and a delivery fee. We drop ten pellets into each barrel every 4-5 days. The need for frequent feeding can cause problems over a holiday period. It has been suggested that these might be overcome by using a commercially-available device designed to deliver a daily food ration to aquarium fish. Kept at a mean temperature of 27oC (range 26-28oC) and a mean humidity of about 50% (range c. 35-65%), mosquitoes in the barrels take up to three weeks to complete their life cycle. Development is much slower at room temperature.
Cultures can be maintained in barrels for long periods with little effort, so that a few mosquitoes of any stage are available whenever they are needed; but when large numbers of larvae are required, all of the same age and in uniformly good condition, we rear separate cohorts in washing-up bowls. Ten egg rafts taken from a barrel culture are placed in a plastic washing up bowl (40 cm long by 30 cm wide and 20 cm deep) one-third full of water. We use white bowls so that the young larvae can be seen easily. The larvae have usually hatched by the next day and can be seen as tiny, light grey threads. At this stage they can acquire oxygen through the cuticle and no air supply is required. The next day a little food is added and a gently-bubbling air stone placed in the bowl. The rate of air supply can be increased gradually as the larvae grow, but the bubbles should never be vigorous enough to agitate the larvae. If the liver/yeast/sucrose diet is used, a pinch is added to each bowl every day, and each cohort will develop from egg to pupa in about five days. Underfeeding results in uneven, delayed larval development and small adults that do not lay eggs; overfeeding produces a foul-smelling brew. On the guinea pig food diet the larvae seem to develop a little more slowly but the amount of food is less critical. One advantage of the guinea pig food diet over the liver/yeast/sucrose diet is that there is no need for an air line into the bowls, although it may be advantageous to supply one if available. In the absence of an air line a surface scum somearial develops on the water but this can be removed by laying a paper towel over the water surface, allowing it to come into contact with the scum and then pulling the towel away sideways, avoiding contact with the side of the bowl. If the cohort is well fed, any larvae that have not been used in experiments will all begin to pupate within a day or so of one another. If further egg rafts are needed to keep a continuous supply of cohorts in production, any pupae remaining unused in the cohort bowls are transferred into an 'oviposition pot', a one-pint disposable plastic beer glass. Each beer glass should contain about 150-200 individuals. With such a high density of adults in a confined space, mating is frequent and large numbers of egg rafts will be laid in the pot. Overcrowding should be avoided because too much contamination of the water surface with cast pupal cuticles and other debris may discourage egg-laying. For transfer to the beer glass, pupae are removed from the cohort bowl by pouring its contents through a tea strainer, and they are put in the beer glass together with about 20 ml of their rearing water. By pouring fresh water through the tea strainer to dislodge the larvae and pupae, the glass is filled about half full. A single sheet of white toilet tissue is hung over the edge of the glass with one end in the water, to give the adult mosquitoes a surface on which to rest and to mate. A saucer (preferably a glass one) resting on top of the beer glass prevents the adults from escaping (fig. 2). If the age structure of the cohorts is uneven (and this happens somearial with all the diets used), it is necessary to select individuals uniform in age as parents for the next generation, because if small larvae are kept with the developing pupae they will die, decompose, and foul the contents of the beer glass, discouraging egg-laying. When the age structure is not uniform, we use a plastic Pasteur pipette (with the tip cut off to give it a wide mouth), or a 50-ml syringe with a short length of polythene tubing attached to the end, to pick out pupae individually from the cohort bowl, leaving the larvae behind. The pupae are put into a plastic beer glass as before, together with pupae from several other cohorts, to produce a batch in which good numbers of adults emerge simultaneously. Adults emerge after 2-3 days. Males (which have feathery antennae) emerge first, and females usually emerge about a day later. The period between adult emergence and egg-laying is about 3-4 days. Some people allow the adults to feed on 10% glucose solution or soaked sultanas. This is not essential but it may help to encourage egg-laying. If the sugar solution is left for more than a day or two it will ferment. If the water in the oviposition pot becomes foul, it may be necessary to change it after most of the adults have emerged but before the eggs are laid. The trick of doing this without releasing the adults is to tilt the beer glass (with the tissue side uppermost), keeping the liquid in by holding the saucer firmly in place. The tilted glass is then partially immersed in a bowl of water, and the dirty water, plus any remaining larvae, is let out by sliding the saucer and slowly raising the beer glass. So long as any gaps are below the water surface, no adult mosquitoes can escape. The glass can be refilled by submerging it in a bowl of clean water and again displacing the saucer a little. With practice considerable control can be exercised and no adults escape. The egg rafts are white when first laid, but within an hour or two they darken and eventually they become charcoal black. The egg rafts can be removed daily by the method described above for changing the water in the beer glasses; the glass is rocked gently from side to side to prevent the egg rafts from adhering to the sides of the glass, and care is taken to keep the rafts floating upright, because shipwrecked rafts do not hatch properly. After transfer from the beer glass to a bowl, the rafts can be scooped off the surface of the water in a white plastic spoon and used to set up new cohorts. A single beer glass usually produces about 50 rafts in all; our record is total of 160 egg rafts in one glass over 3 days.
With large numbers of uniformly-aged last-instar larvae or pupae, it is possible to conduct experiments on the effectiveness of control agents less toxic than conventional insecticides. Since the early use of oil films on water to control mosquito larvae, insoluble surface-active agents have been developed further and are among the more environmentally acceptable methods of control for the aquatic stages of mosquitoes. The mode of action is uncertain, but there are three ways in which these agents might kill mosquito larvae: by interfering with the surface tension effects on which gas exchange at the water surface depends; by flooding the tracheal system; or by direct toxicity. We have tried to find cheap, readily available materials that form a surface film on water and that could be used to treat water butts and other small water bodies in and near houses in regions where technically elaborate control operations are not practicable. Plant-derived oils, such as eucalyptus oil, have proved promising. Using disposable 40-ml pots (clear plastic 'one-ounce' tubs with lids, sold by Concept Catering, 1 Duncock Lane, Elsworth, Cambridge CB3 8JL, @ 67.50 per thousand), each containing 20 ml tapwater giving a surface area of about 16 cm2, we set up an experiment with ten last-instar mosquito larvae per pot and five pots per dose, testing a range of doses (1,2,4,8 16 microlitres) of oil run carefully onto the surface of the water after the larvae had been put in. The pots, with their lids on, were kept in an incubator at 30oC for 24 h, at the end of which larvae in each pot were scored as 'dead' (motionless, even when disturbed by gently jogging the pot) or 'alive' (capable of moving). From the count of dead larvae in each pot we could calculate the 24-h LD50, the dose that kills 50% of larvae in 24h, by plotting the mean number dead at each dose on a probability scale (corresponding to a cumulative normal distribution scale) against dose of oil on a logarithmic scale. This is easily done using special graph paper known as probit paper, with a logarithmic scale on the x axis and a probability scale on the y axis. The mathematical basis is explained by Garvin (1986) and Sokal and Rohlf (1981). The plot produces a straight line from which the dose corresponding to 50% mortality can be read off. This graphical method generally gives an adequate estimate of the LD50, but if a more accurate estimate is required the LD50 can be calculated from a probit regression using a computer programme such as Generalised Linear Interactive Modelling (GLIM) (Atkin et al., 1989) or by a time-consuming manual calculation (Busvine, 1971). On the basis of the LD50, expressed as microlitres per square centimetre, we can compare a range of readily-available oils (somearial spiced with surface-active compounds to increase their ability to spread on the water surface) with surface films marketed commercially for mosquito control, such as Arosurf MSF. Experiments might be designed along similar lines to see how susceptibility to these control agents varies through the life cycle of the mosquito. Our aim has been to find a control agent that is inexpensive, readily available in rural areas, and of low toxicity to humans and other non-target organisms. Some oils can be seen to enter the gas exchange system of the mosquito larvae, flooding the tracheae and giving them a translucent appearance under a stereoscopic microscope, instead of the opaque silvery look they have when filled with air. Mosquito larvae in oil-treated pots frequently nibble at the snorkel-like siphon at the tip of the abdomen, as if attempting to remove a contaminant. If these oils kill larvae by interfering with gas exchange between the atmosphere and the tracheal system, we might expect that they would kill mosquito larvae faster in stagnant waters rich in decomposing organic material, where dissolved oxygen is in short supply, than in well-oxygenated waters. This possibility might be explored by comparing the effectiveness of a chosen oil on water deoxygenated by boiling with its effectiveness on well-oxygenated water. The difference may be more obvious with young larvae, which derive more of their oxygen from solution in the water, than with large larvae, or pupae, that depend more on atmospheric oxygen.
Mosquito larvae and pupae divide their time between resting, tail up, at the surface, and diving down below the surface. They alter the allocation of time between these two activities in response to certain compounds applied to the surface of the water, changing the mean frequency or the mean duration of dives below the surface. Detailed behavioural effects of this kind are difficult to monitor directly in a crowd of active mosquito larvae, but can easily be quantified if a group of, say, five or ten mosquito larvae is filmed on video, preferably with a time signal shown on the tape. The film can be made and analyzed using ordinary home video equipment. We use a clear plastic rectangular box in which we have improvised five vertical compartments so that individual mosquitoes are kept apart but all five can be filmed at the same time through the flat wall of the box. One might, for instance, film the larvae for five minutes, then add a surface oil, then continue filming for a further five minutes. By scoring the number of larvae at the surface, the number of dives and the mean duration of a dive for each successive minute, it is possible to see how surface treatments affect the probability of diving (number of dives, per mosquito at the surface, per minute) and the mean duration of a dive (or of the period at the surface between dives). Sih (1986) has suggested that mosquito larvae alter their dive timing in the presence of certain predators, perhaps reducing their vulnerability by spending less time in the region where predators are most likely to find them; and that this predator effect is mediated by a water-borne chemical. Video filming could be used to explore effects of this kind. If insoluble surface-active agents disrupt the surface forces that enable mosquito larvae to hang at the water surface, these agents may be expected to be equally damaging to other insects that depend on surface forces. Guthrie (1989) describes the natural history of some surface-dwelling insects and outlines methods for exploring the effects on them of contaminants that alter surface forces. Among these surface-dwelling insects are predators such as the water boatman or backswimmer, Notonecta, that feed readily on mosquitoes, and are regarded as important natural control agents in, for example, rice fields in the southern United States. If these predators are harmed by surface-active mosquito control agents, the natural control exercised by their predation may be sacrificed. Studies on the predatory behaviour of such insects, in clean water and in the presence of surface-active contaminants, can be valuable. The bacterium Bacillus thuringiensis israelensis is used as a mosquito control agent, somearial in combination with a surface-active agent that helps to hold the bacteria at the surface where the mosquito larvae will contact them. These bacteria are effective when eaten by mosquito larvae. It is therefore important to study feeding behaviour. Information available so far is reviewed by Merritt, Dadd and Walker (1992) and Clements (1992), but much remains to be discovered about the factors that determine the rate of feeding and the way a larva allocates its time between feeding at the surface (where it may pick up bacterial spores), filtering in the water column and browsing on the bottom. Some compounds have already been shown to increase feeding rate; perhaps others may be found to decrease it, causing starvation. One way to investigate the rate of feeding is to feed larvae on a suspension of coloured particles (such as Indian ink, or carmine particles) for known periods of time, and monitor the movement of this coloured material along the gut by examining larvae under a stereoscopic microscope at intervals. The position of the visible boundary between the original food and the coloured particles can be recorded in terms of the number of segments along the body. It would be interesting to see whether adding, for instance, dried powdered yeast to the water will stimulate feeding, making this boundary move faster down the body. If the larvae are non-selective filter feeders, ingesting particles of a given size regardless of composition, it might be possible to control them by adding to the water a suspension of inert, non-nutritious particles of the appropriate size, preventing the larvae from obtaining a nutritious diet. Even if inert particles are not normally eaten, they may be taken if flavoured with a compound that acts as a feeding stimulant. Marmite-flavoured kaolin or talcum powder would be a novel control agent! Safe, effective mosquito control is a matter of life and death to many people in the tropics. Particularly needed are control methods that can be operated by local communities on a small scale without the intervention of professional agents or expensive spraying machinery (see Curtis, 1991). The development of cheap, simple, practicable community control methods of this kind depends on careful exploration of mosquito biology, coupled with imaginative lateral thinking. A disadvantage of some of the investigations suggested here is that they involve killing mosquitoes, and some people may feel reluctant to do this, especially after studying their exquisite complexity under the microscope. On the other hand, in countries where mosquito-borne diseases cause serious human suffering and death, mosquito control is considered essential; conventional control may be ineffective because so many races of mosquitoes have developed resistance to insecticides, which may cause high mortality among non-target organisms. Serious, careful research that provides the foundation for more specific and biologically based control methods can benefit both people and the environment. The study of mosquitoes is not only worthwhile, but also fascinating, and the books by Clements (1993) and Snow (1991) have recently made the field accessible by providing a firm base and making it possible to set individual studies into the context of existing knowledge.
We are very grateful to Barbara Sawyer (London School of Hygiene and Tropical Medicine) for her valued help and advice, Stuart Green for guidance, Philip Corbet and Michael Reiss for commenting on the text, and many students whose ideas and enthusiasm have sustained the mosquito project over the years.
Atkin, M., Anderson, D., Francis, B. and Hinde, J. (1989) Statistical modelling in GLIM. Oxford: Clarendon Press. Brookfield, J. F .Y., (1991) Molecular evolution: the resistance movement. Nature 350,107. Busvine, J. R. (1971) A critical review of the techniques for testing insecticides. Slough, Commonwealth Agricultural Bureau. Clements, A. N. (1992) The biology of mosquitoes. Volume I Development, nutrition and reproduction. London: Chapman and Hall. Curtis, C.F. (1991) Control of disease vectors in the community. London: Wolfe Publishing Ltd. Garvin, J.W. (1986) Dealing with data. Vol. 1. Cheltenham: Stanley Thornes (Publishers) Ltd. Guthrie, M. (1989) Animals of the surface film. Naturalists' Handbooks 12. Slough: The Richmond Publishing Co. Ltd. Laird, M. & Miles, J.W. (1985) Integrated mosquito control methodologies. Volume 2. Biocontrol andother innovative components, and future directions. London: Academic Press. Merritt, R.W., Dadd, R.H. & Walker, E.D. (1992) Feeding behavior, natural food, and nutritional relationships of larval mosquitoes. Annual Review of Entomology 37, 349-376. Sebastian,
A., Sein, M.M., Thu, M.M. & Corbet, P.S. (1990) Sih, A. (1986) Antipredator responses and the perception of danger by mosquito larvae. Ecology 67, 434-441. Snow, K. R. (1990) Mosquitoes. Naturalists' Handbooks 14. Slough: The Richmond Publishing Co. Ltd. Sokal, R.R.
and Rohlf, F.J. (1981, 2nd edition) Biometry. New York: W.H. Freeman
and Company. |
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