Re: how do flies drink

    The common house fly has an interesting tongue.  At one end it has a soft
spongy suface that 
sucks up liquid food.  They eject digestive juices out of their mouth and then
sponge it back up 
with digested food from the suface of what they are eating. Kind of gross, eh?
If you have ever 
watched a fly, they dab their spongy tongues up and down on the surfaces they
land on and look 
like a dog lapping up water. They also drink water that way.  
     That is also why some flies in Australian are so very annoying!  They try
to sit at the corner of 
your eyes, mouth and nose and sponge up moisture from them.  They do this to
other animals 
and are annoying to them too.  As Australia has areas that are very dry, this is
a way for flies to 
survive.  But we humans don't like to have flies sitting on our faces, so we
contantly wave them 
away or wear kookie hats with corks hanging down from the brims.  Of course only
visitors to 
Australian wear those kookie hats. 
      We also see this when we see sick people in Africa with flies sitting  on
their faces because 
there are too many flies  and  they are too weak to wave them away. 

Here is another post at Mad Scientists on insects drinking water:
http://www.madsci.org/posts/archives/dec99/945089340.Gb.r.html

Info and pictures of mouth parts:
http://insected.arizona.edu/flyinfo.htm

Microscopy picture of fly mouth parts 

http://www.microscopy-uk.org.uk/mag/artfly/eat.html