A Butterfly’s Tongue

What am I looking at?

This is the proboscis of a butterfly. It is composed of two long galeae (1 and 2) that enclose a central food canal (not visible). There are also sensory hairs (3) lining the proboscis; these contain odorant receptors, which help the insect detect smells and thus find food. The large orb in the top right corner is the butterfly’s eye (4), and the purple spikes surrounding it are scales on the butterfly’s head (5). Click on the right arrow to see a closer view of the proboscis.

Biology in the background

There are several species of butterflies, plus the whole Saturniidae family of silk moths, that don’t feed and that lack mouthparts as adults but instead spend all their short lifespan (just one to two weeks) looking for a mate, mating, and laying eggs. Most that do feed use their proboscis to suck liquid nectar from flowers. When they aren’t feeding, their proboscis is curled up underneath their head, as seen here.

When they find a flower, they unroll their proboscis and stick it as far down the flower as they can to access the nectar there. Then they suck the nectar up through a hollow food canal within the proboscis. The suction is provided by muscles surrounding a hollow sack in their head that’s connected to the food canal, aided by capillary forces.

Such proboscises can vary in size a great deal. The longest, in the Wallace’s sphinx moth, can reach 28.5 centimeters – almost a foot long. The existence of this moth was predicted by Darwin and Wallace based on the incredible length of the nectar tube of a certain species of orchid in Madagascar. Their prediction was proven right in 1903, 12 years after Darwin’s death.

Technique

These images were created using scanning electron microscopy and then colored to highlight the different biological structures in the images.