Butterflies drum, but not in a band.
One way a butterfly finds a larval food plant is to “drum” the leaf.
The butterfly is not looking for food for itself but instead settles for brief moments on leaves. Upon close examination it is seen to “drum” on the leaf with its forelegs. The tips of the forelegs are equipped with chemoreceptors, which can detect traces of chemicals that indicate whether this is or is not a leaf that could feed its larvae. On average a female butterfly may visit up to 10 possible host plants before picking the perfect one. If satisfied it then lays its eggs on that plant. This ensures that the caterpillar has food immediately after it hatches and does not waste energy looking for it.
Each species of butterfly have certain plants that support their larvae.The larvae will only eat specific host plants and nothing else.This reduces competition for food and gives all a better chances for survival. In our F. Jean McLeod Butterfly Gallery you can see this behaviour in our swallowtail butterflies as they circle the fruit feeders when we serve oranges.
Look for some of these plants outside to see if eggs have already been laid or if you catch a female butterfly “drumming”:
Viceroy Butterfly - Willow
Monarch - Milkweed
Painted Lady - Thistle and Lupine
Mourning Cloak - Willow and Elm
Common Hairstreak - Hops
Fritillary Butterfly - Violets