How Do Mosquitos Change Their Behavior?

[CraigD]

I heard an interesting claim made by an expert on mosquito-transmitted diseases: that the most effective barrier to malaria transmission in recent history has been insecticide-treated bed nets, but that their effectiveness has diminished because mosquitos changed from feeding on sleeping people to feeding on them during the day, when they’re outside of their bed nets.

 

That got me thinking - how does a population of tiny animals with a tiny nervous systems that where adult individuals live for about 7 days change their behavior? It seems impossible that individual female mosquitos learn in some intellectual or trial-by-error way.

 

The only answer that makes sense to me is that, in mosquito population, there are at all times genetically-defined sup-populations that feed at different times of the day and place ranges. The reproductive success of each generation, and thus their percentage of the total population size, depends on their environment. IBNs, though artificial, are an environmental factor, which cause the mosquito subpopulation with “feed on people in bed” genes to dwindle, while that with the “feed on people before they go to bed” swells.

 

It seems the maxim “there is no biology but evolutionary biology” applies not only to the long-term evolution of species, but to their week-to-week behavior.

[NotBrad]

-snip-

I have always been very interested in topics such as these, i.e the more practical and applicable side of science. There are still many things we don't fully understand and this is one stellar example of just how amazing(albeit gross too) our world can be. I am also quite glad for the bug screens on the doors and windows of my house now. Don't know why, but the idea of mosquitoes stabbing a disgusting disease riddled proboscis into me, drinking my blood, and injecting me with digestive juices seems to bother me more than anything else. These disgusting little bastards should be wiped out to prevent the spread of malaria.

[billvon]

I have always been very interested in topics such as these, i.e the more practical and applicable side of science. There are still many things we don't fully understand and this is one stellar example of just how amazing(albeit gross too) our world can be. I am also quite glad for the bug screens on the doors and windows of my house now. Don't know why, but the idea of mosquitoes stabbing a disgusting disease riddled proboscis into me, drinking my blood, and injecting me with digestive juices seems to bother me more than anything else. These disgusting little bastards should be wiped out to prevent the spread of malaria.

. . . at which point we would discover what other animals and plants depend on them.  You can't change just one thing about an ecosystem.

[CraigD]

These disgusting little bastards should be wiped out to prevent the spread of malaria.

I don’t think it’s likely that mosquitos will be wiped out worldwide by any human activity. As long as even a few of them can carry out their life cycle, even if we reduce their population by 99%, such as via draining and spraying standing water, they’ll bounce back within a few years if we stop. The main impact of humans on mosquitokind is helping them spread to places they otherwise couldn’t have reached, such as islands.

 

Mosquitos can live almost anywhere with liquid water. If there are humans with malaria in their blood around, a few (about 100 of about 3500 known) species of mosquitos can spread it to other humans. Like many parasites, only a few (5 of over 200 known) species of malaria can infect humans, and 4 of those can infect only humans (one, Plasmodium knowlesi, can infect both humans and monkeys). Other species infect other primates, still others can infect pretty much anything with a liver and blood, including birds and reptiles.

 

While I doubt we can make mosquitos globally extinct (without making ourselves extinct in the process) there are a couple of interesting events in the history of mosquitos that hint at how we might better make them locally extinct.

 

Ireland has few mosquitos, none of them capable of spreading malaria to humans. Before the Little Ice Age, ca 1650, this wasn’t true. So brief extreme cold periods can wipe out the human->mosquito->human malaria vector.

 

Iceland doesn’t appear to have any mosquito species at all, a scientific mystery.

 

. . . at which point we would discover what other animals and plants depend on them. You can't change just one thing about an ecosystem.

Ireland and Iceland seem to have done OK ecologically without the dangerous-to-humans mosquito species, so I’m not too worried about the impact of a few mosquitos species’ extinction.

 

Also interesting is the origin of malaria in humans. It may have evolved along with humans, but some recent studies suggest we were malaria-free for some perhaps a million years or so, then re-acquired the human malaria species from one evolved from gorillas.

 

In both these places, other flies have filled the missing mosquitos’ niche. Nature excels at niche-filling.

 

Sources: Why are there no mosquitos in Iceland, when they live on both sides of Greenland?, Cover up: the mozzies are near (about mosquitos in Ireland), Do all mosquitoes transmit malaria?, Malaria in Humans Traced to One Infected Gorilla.