hi, whilst observing the bees and insects in my garden alighting upon my hardy geraniums, I have two questions: Firstly, why do pollen collecting insects choose certain flowers over others from which to collect pollen? Secondly, does each insect only collect a small amount of pollen from each flower, therefore leaving enough for other visitors, or does the flower constantly produce pollen throughout the day? Thank you

foraging strategies for bees are complex and well researched (google "foraging strategy bees"). The wikipedia link below and references therein is also a good starting point
http://en.wikipedia.org/wiki/Bees_algorithm

As to flowers and pollen production - the amount an individual bee or other insect takes will be a small fraction of the total. I don't know much about pollen production by plants but would assume it will vary between species and will most likely be a continuous production during the day.