I have heard of a theory on this topic (limiting factors). It is known as LIMITS OF GROWTH by Club of Rome. Experts are of the opinion that this is accepted to be obsolete now. This theory is explained in relation to a wild environment where everything happens in the natural way and so the population of no species grow too much or too less than what is required for the harmonious co-existence of the collection of life forms there.
In the modern situation there is one life form which does not obey many of the rules & laws of nature. This is known as HUMANS. It manipulates things to its advantage. This is the root cause of all problems and disrupts the harmony essential for the peaceful co-existence.
God has implemented different schemes to control the population of various species and also to maintain the quality of each population.
Death due to ageing is the foremost among those.
Another one is predators.
Diseases' (leading to death) is yet another.
Next one is regulating reproduction. Most of the animals and birds have limited reproductive cycles - annually two or one, or even less. Elephant reproduces once in several years. Its gestation period itself is about two (2) years and produces not more than one offspring at a time. Lion and tiger, even though reproduce once in few years only, gives rise to 3 or 4 cubs at a time. Cattle (cow, buffalo etc) have gestation of less than a year and very rarely only get more than one calf at a time. Mother cow become reproductive in a few months from then. Sheep, goat, dog, cat, squirrel etc have smaller gestation periods but usually produce multiple offspring almost once in an year. Rabbits, poultry etc have more than one reproductive cycle every year and each time produce multiple offspring. Rabbit's gestation period is only twenty eight (28) days and mother becomes reproductive in a few days. But as they are prey to several predators, their population never grow beyond limits.
In the case of humans several factors other than natural are actively present. Some of them are social, education & awareness, attractions like monitory/other incentives etc. In present society a pair of human beings takes 20-25 years for doubling. Where as in the case of mosquito the growth in 1 month itself is a phenomenal 5000-15000 %!!! Such a high rate of reproduction is provided to ensure the availability of a healthy and dynamic mosquito population every where even under adverse circumstances and environments and also to ensure that there will be no threat of extinction what so ever.
Since it is a very essential TOOL of God, as a safe guard against extinction of mosquitoes God have created large number of species of them with diverse qualities. Even though there are different opinions about their number, there is no doubt that it is well above 2000 (because The Encyclopedia Britanica said there are 2500 species of mosquitoes, the American Mosquito Control Association said 4000 and The Wikipedia said (http://en.wikipedia.org/wiki/Mosquito#Evolution) 3500). Of late we find more species of mosquitoes acquiring vectorial abilities (eg. Aedes Albopictus in 2005-2006 in Reunion Island through mutation of chikungunya virus) http://en.wikipedia.org/wiki/Chikungunya#Epidemiology . This too is a safe guard against probable unavailability of vector/carrier mosquitoes - a futuristic plan of action of God Almighty!
But the very high rate of growth can result in its over population. It is to check this risk that the powerful limiting factors are introduced in their life cycle.
Water is the first and foremost among them. Unavailability of water certainly terminates mosquito's life cycle. Hatching process of mosquito's egg will not get triggered unless & until it come in contact with water. Aqua contact is inevitable to progress it as well.
Next limiting factor is predators.
Dragon fly is a very prominent one among the predators of mosquito. They catch flying mosquitoes & eat. It is an ancestral enemy of mosquito. What I mean to say is that during all the phases of mosquito's life cycle the dragon fly is a predator. (Dragon fly also lay egg in water. Its offspring - NYMPH - lives several months in water and feeds on mosquito larva. Every day each nymph eats dozens of wrigglers.
Another predator is fish. In the pre-insecticide period fish was a very prominent mosquito control tool. With the advent of DDT they were pushed to the back stage.
In India itself there are dozens of fish species that had been utilised for this purpose. There was very clear idea about the qualities these fishes had to have. Some of them are:
robustness/ruggedness, easily portable, fast multiplying, no food value for humans, small enough to reach narrow spaces to follow & catch wrigglers, surface feeders to ensure proximity to wrigglers, so on and so forth.
They fall prey to spiders & lizards also.
Sparrows are also reported to feed occassionally on them.
Water being bounded always, limits their freedom of movement (in contrast to their adult phase) and make them easy prey to fish & nymph.
Another limiting factor is their own feeding. Females of them feed on warm blooded creatures including humans. The feeding process causes itching to the victim and may end up in the premature death of that mosquito by the angry reaction of the prey.
Yet another limiting factor is the dependence of growth duration on environmental temperature. The life span in water that takes only one week in hot climate can get extended to three weeks (300%) in cold climate.
In snow covered regions like Alaska (the 50th state of USA), they get hardly two months to live and reproduce. This is because during those months only, water (generated by melting of snow/ice due to sun shine) will be available to hatch their eggs and complete their larva & pupa phases.
It is in spite of all these limiting factors that the mosquito menace keeps growing from bad to worse year after year and throwing human life from frying pan to fire.
We have succeeded in capturing the outer space, landing on moon, so on & so forth. Now a days affordable people are choosing moon/outer space as their tourist destinations. But alas, we are miserably failing in capturing this tiny little insect. At this point of time I am reminded of 4 things: a proverb, two jokes & a parable. I reserve them for future.
As promised earlier I am uploading the graph of malaria data of Keralam.
*The upload got discarded! Response was You must join a group for uploading a picture. The link provided took me to an empty space! What to do now?
A little more on limiting factors ...
This is in continuation of previous reply.
In the modern situation there is one life form which does not obey many of the rules & laws of nature. This is known as HUMANS. It manipulates things to its advantage. This is the root cause of all problems and disrupts the harmony essential for the peaceful co-existence.
Since it is a very essential TOOL of God, as a safe guard against extinction of mosquitoes God have created large number of species of them with diverse qualities. Even though there are different opinions about their number, there is no doubt that it is well above 2000 (because The Encyclopedia Britanica said there are 2500 species of mosquitoes, the American Mosquito Control Association said 4000 and The Wikipedia said (http://en.wikipedia.org/wiki/Mosquito#Evolution) 3500). Of late we find more species of mosquitoes acquiring vectorial abilities (eg. Aedes Albopictus in 2005-2006 in Reunion Island through mutation of chikungunya virus) http://en.wikipedia.org/wiki/Chikungunya#Epidemiology . This too is a safe guard against probable unavailability of vector/carrier mosquitoes - a futuristic plan of action of God Almighty!
But the very high rate of growth can result in its over population. It is to check this risk that the powerful limiting factors are introduced in their life cycle.
Dragon fly is a very prominent one among the predators of mosquito. They catch flying mosquitoes & eat. It is an ancestral enemy of mosquito. What I mean to say is that during all the phases of mosquito's life cycle the dragon fly is a predator. (Dragon fly also lay egg in water. Its offspring - NYMPH - lives several months in water and feeds on mosquito larva. Every day each nymph eats dozens of wrigglers.
Another predator is fish. In the pre-insecticide period fish was a very prominent mosquito control tool. With the advent of DDT they were pushed to the back stage.
In India itself there are dozens of fish species that had been utilised for this purpose. There was very clear idea about the qualities these fishes had to have. Some of them are:
robustness/ruggedness, easily portable, fast multiplying, no food value for humans, small enough to reach narrow spaces to follow & catch wrigglers, surface feeders to ensure proximity to wrigglers, so on and so forth.
They fall prey to spiders & lizards also.
Sparrows are also reported to feed occassionally on them.
Water being bounded always, limits their freedom of movement (in contrast to their adult phase) and make them easy prey to fish & nymph.
In snow covered regions like Alaska (the 50th state of USA), they get hardly two months to live and reproduce. This is because during those months only, water (generated by melting of snow/ice due to sun shine) will be available to hatch their eggs and complete their larva & pupa phases.
We have succeeded in capturing the outer space, landing on moon, so on & so forth. Now a days affordable people are choosing moon/outer space as their tourist destinations. But alas, we are miserably failing in capturing this tiny little insect. At this point of time I am reminded of 4 things: a proverb, two jokes & a parable. I reserve them for future.
*The upload got discarded! Response was You must join a group for uploading a picture. The link provided took me to an empty space! What to do now?