[Lewis Thomson (OP)]

Charles has done an experiment but doesn't know why the results are the way they are.

"I leave
a) Diluted Robertsons Barley water
b) A mug of tea
c) A pot of coffee

Why do by far the greatest number of drosophila (flies) drown in the coffee (Black no sugar) ?"

Can you help explain the results in the comments below.