Insects visit the flowers in search of nectar, which is
located at the bottom of the flower tube. This means that only long-tongued insects can
actually reach the nectar in the base.
An insect such as a Brimstone butterfly
(Gonepteryx rhamni), visiting a pin-eyed flower, gets pollen stuck to the middle of
its proboscis from the anthers half-way down the flower tube. If it then goes to visit a
thrum-eyed flower, the pollen is perfectly positioned to be wiped off on the stigma, in
this case, halfway down the flower tube.
The reverse is also true. If the
butterfly first visits a thrum-eyed flower, pollen is wiped off onto the top of its
proboscis as it searches for nectar. This is then ideally placed to be transferred onto
the stigma of the next pin-eyed flower which it visits.
If it is spring time, why not go out
and see how many Primroses you can find near you. Are the flowers thrum or pin-eyed? Can
you see any insects in them? Why not watch for a while to see if you can catch a glimpse
of some of the year's earliest butterflies coming to take advantage of their nectar. Do
any other insects visit the flowers?
Just sitting quietly and watching can
often reveal fascinating things!