Generally speaking,mosquitoes are not the best insects to have around.Though beneficial for their pollination activities, the female anopheles mosquitoes have been a complete nuissance to mankind for over 2000 years! Eventhough insects have been known to be around for several million years,with about 2050 species,it would be difficult,at least for now,to compare completely their lifestyle before the advent of man and now that mankind is habiting the planet earth.For now,and perhaps,adaptation and evolution are two reasons one can give.
To approach this discourse in the proper sense,the behavioral habits of both the male as well as the female mosquitoes of common species was investigated .Today,the commonest species of mosquito include aedies,culex and anopheles.Research shows that while all species participate in pollination of flowers for their nectars,fruits and saps for their sugar, the female anopheles mosquitoes usually get an aditional responsibility to suck blood.But why is this so? The following are the reasons why this species of mosquitoes is so fond of blood meal:
1.The male has a reduced mouthparts
A careful look at the mouthparts of the female mosquitoes reveal a hypodermic mouthparts which enable them to pierce the skin and suck the blood of other arthropods,reptiles,birds,
and mammals.In these insects, all mouthparts are elongated. The labium encloses all other mouthparts like a sheath. The labrum forms the main feeding tube, through which blood is sucked.Mandibles and maxillae occur in pairs, together forming the stylet, which is used to pierce an animal’s skin.The labium remains outside the food item’s skin, folding away from the stylet,during piercing. And the saliva,containing anticoagulants, is injected into the food item and blood is sucked out, each via different tubes.However,the males have reduced mouthparts(or proboscis) and feed instead on nectar,fruit,sap, and water.Again,the earliest insects had chewing mouthparts,and evolution,is one reason for this new trend!
2.Special sense of smell for warm and cold blooded animals
The female anopheles mosquito has a special sense of smell specifically devoted to blood.This is an innate behavior which allows the insect to feel both the sweat and the carbon dioxide gas exhaled by man,from a distance,as far as 90 feet away,even more! This behavior is not observed in the male,eventhough both genders are known,generally,like other insects,for their long sense of smell.
3.Maintenance of reproductive cycle
Only the female mosquitoes reproduce,and blood is required to maintain the reproductive cycle,and hence protoplasm(or living cells),until the larvae are hatched.To the female mosquito,a blood meal is a supplementary diet.Blood contains iron,vitamins,water,and more importantly,protein,which,being an organic polymer,could be broken into their respective amino acids.These nutrients,act in a myriad of ways to assist the various developmental stages of the egg,shell formation inclusive,and the subsequent growth to become a larva.While this option may look good to the mosquito,at least to consolidate the overall number of eggs converted to larvae,its life span is reduced, as it gets tired out after the blood meal.In short,it becomes less active.
Finally,the female mosquitoes have become a necessary nuissance in our lives.Truly,they suck blood,because they have a special mouthparts called stylet,a sense of smell distinctly for both warm and cold blooded animals,and have to maintain their reproductive cycle using bloodmeals.
Reference
http://encarta.msn.com/media_461517520_761565501_-1_1/female_mosquito_sucking_blood.html
http://www.backyardnature.net/insmouth.htm
http://www.lanakids.com/mosquito.html
