Why do mosquitoes attack just as we are drifting off to sleep? Does
the body change in that drifty state before sleep in some way, such
that the mosqutio senses it and attacks at the most infuriating point
possible?

I think it has more to do with the time of day that mosquitos are most active.

HAHHA...

http://ioannis.virtualcomposer2000.com/writing/OnMosquitos.html

It's not just that they are active at night, it's that they are in
your room and they hide somewhere. You go looking for them and can't
find them. You give up, turn off the light and start going to sleep.
If it takes you 5 minutes or 15 minutes to go to sleep, still they
don't attack. But JUST as you are going into that sleepy hazy state
before you go to sleep, they attack. It happens every time! This is
the mystery I am trying to solve.

I understand they are attracted by carbon dioxide in your breath.

I would guess that, as you are about to go to sleep, you have finally
settled down and stopped tossing and turning and therefore
interrupting the steady stream of exhaled air - allowing the pesky
critter to easily home in on you.

That's a very smart answer! You could be right. I will have a look to
see if there are any articles about that.

Gotta agree with murunbuchstansinger-ga I once had the local council
(NSW Australia) come and set traps in the reserve adjoining our house.
The traps were made attached to a CO2 bottle which leaked the C02 into
the trap. They were looking to see how many mozzies carried the Ross
River Virus.
Cheers,

murunbuchstansinger is right. Mosquitoes do get attracted by the CO2
that the living organisms exhale. There are some other factors that
contribute to it as well. These include body heat, moisture and scent.
However, CO2 is the single most important reason known so far to
researchers. Most of the mosquito traps either use refillable
cylinders or some filament that can produce or dispense CO2 at a high
rate.

Mosquitos are not attracted to us because they know that we are going
to sleep but because when we stabilize at one place, the concentration
of CO2 increases significantly at that location. Mosquitos get
attracted to the higher levels of CO2 and hence flock to that
position. If you try to stand at a place without much movement, you
will see a lot of mosquitos coming your way.

There is another little experiment you can do. If you happen to go to
a place where there are a lot of mosquitos, duck your head to the side
of a tall person's head and you will see that the mosquitos will leave
you and start hovering around the other person's head. This is because
when you do that, the level of CO2 at that place increases
significantly.

Hopefully, my comment will help.

Thanks - that is helpful. It makes a lot of sense. I wonder if wearing
a muzzle would do the trick?!

How about a mosquito net ?

After living in a tropical climate for a year, I found that mosquitos
virtually dissapear when there is a slight breeze present; the same
principle applies in the bedroom when one turns on an overhead fan set
on low.

I didn't know the reason for this (thought their little wings couldn't
handle the wind I suppose), but after reading about the CO2 attraction
in these posts, it all makes sense now. The fan/wind must sufficiently
disperse the CO2 in the local area so that the mosquito can't get a
fix on you.

thanks

The CO2 is what attracts them from a distance, but once they're within
a couple feet of you it is your body heat that attracts them. As they
get closer to the source of heat and CO2 they home in on the hottest
points, i.e your blood vessels and go to town. Interesting fact, it's
only the females that bite...typical.

HI,

  When you are clear-headed,your body are keep moving everywhere,and
the mosquitoes can landing on your body to attack.You can aware the
attack clearly when your are clear-headed.
  When you are drifting off to sleep,your mind is restrain,your brains
are become slowness and not aware of the change of the environment,and
you are not moving everywhere.So the mosquitoes can landing on your
body,attack your arms or legs or nose...
   And when the mosquitoes bitting,it will excrete some matter like
anaesthesia drug.So you cannot feel the pain at the moment.