Eileen Tiller, of Paraparaumu, asks :-
Do butterflies have memories? I notice that monarch butterflies hover over the exact spot in my garden where a swan plant used to grow.
George Gibbs, an entomologist at Victoria University of Wellington's School of Biological Sciences, responded.
A fascinating question that I have been pondering myself lately. Like Eileen, I have noticed a monarch that has been circling around a garden with swanplants for many weeks. The simple conclusion is that these adult butterflies must retain some sort of location memory in order to repeat their flight patterns. This ability is widely known from other insects, especially honeybees and many types of predaceous wasp that can relocate their burrow provided landmark clues remain in the right places. The monarch I have been watching continues to return every day, despite the demise of the swanplant by an over-dose of caterpillars.
But there is more to insect memory than what the adults remember. Some researchers have found that moths can remember experiences that their caterpillars had before metamorphosis. Douglas Blackiston and colleagues (2008) at Georgetown University, Washington DC, have tested whether a chemical administered to a fully-grown caterpillar could be remembered after it turned into an adult moth. They found that it could and thus showed that certain neural connections in the brain could persist through metamorphosis to the adult. This has important implications for the choice of food-plants the moth makes when laying its eggs.
As an aside, it is worth noting that adult monarchs live much longer than many other insects so their memories must play an important role in survival by leading them to good places for sheltering in storms, as well as where to look for a female (if you are male).