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Did you say proboscis?

July 22, 2014

By Kate Davison, Living Conservatory Specialist. The Living Conservatory is an immersive exhibit similar to a Central American dry tropical forest. The permanent exhibit features live turtles, snakes, butterflies and even a two-toed sloth.

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Moths, and butterflies, are both part of the Order Lepidoptera, being scaled, flying insects. Moths comprise roughly 90% of the known species of Lepidoptera, with multiple clades, superfamilies, and families of moths, while butterflies are only about 10% and all are contained within a single Superfamily the Papilionoidea. With some 160,000 moth species it’s no surprise that some moths are more closely related to butterflies than they are to other moths.

Vintage Field Guide of Lepidoptera

Vintage Field Guide of Lepidoptera.

There are several commonly “known” ways to differentiate between moths and butterflies, however there are exceptions to every single method. Many butterflies are brown, such as owl butterflies, and many moths fly during the day, for example urania moths. And the world is rife with examples of moths that typically land with their wings closed, and butterflies who land with their wings open. Really moths and butterflies are much more similar than they are different.

However… we can talk about something nearly everyone likes to do – eat.

Let’s first make it clear that not all Lepidoptera feed as adults. Many Lepidoptera, only feed as larva, the stage also known as the caterpillar. When Lepidoptera do feed as adults they use a mouthpart known as a proboscis. This is a very interesting feeding structure worth learning more about so you can impress all your friends with your intricate knowledge of the lives of, some, Lepidoptera. The adult Lepidoptera who do not feed either have no proboscis or a severely underdeveloped proboscis.

SEM microphoto of the head of a snout moth – note the "snout" (labial palps) extending to the upper left above the proboscis

SEM microphoto of the head of a snout moth – note the “snout” (labial palps) extending to the upper left above the proboscis.

The proboscis is an intricate structure made of two interlocking modified galeae. A galea is a mouthpart in the maxilla of a chewing insect, which typically assists in guiding food into the mouth and cleaning the front of the insect. It was named galea because of the resemblance to a Roman helmet of the same name. In Lepidoptera the galeae have been elongated but the function is still to guide food. The space made between the interlocking galeae is known as the food groove, or food canal. When not in use, the proboscis is coiled close to the head, kept in place by small interlocking parts on the outside of the galeal wall.

Convolvulus Hawk-moth, Agrius convolvuli, with stretched proboscis

Convolvulus Hawk-moth, Agrius convolvuli, with stretched proboscis.

During uncoiling there is an increase in hemolymph pressure through the proboscis, and coiling is accomplished by muscles in outer walls of the galeae; the proboscis in its relaxed state will be coiled. Liquid is harvested from flowers, fruit, and other food sources using a vacuum, drawing the liquid up the proboscis into a reservoir bulb in the head of the Lepidoptera, and then allowing the food to flow into the stomach once the entrance to the proboscis is blocked off and the vacuum released. Not all proboscises are the same either — length, color, and sensilla (sensory organ) number and placement can vary depending on species, and vary to some extent depending on food source.

The proboscis is an intricate, fascinating structure, which members of the Order Lepidoptera use to feed.

Butterfly proboscis in action!

Butterfly proboscis in action!

Want to see a proboscis in action?

Visit the Museum’s Living Conservatory where live butterflies accompany you as you explore. Filled with tropical plants and animals, the Conservatory recreates the sights, sounds and smells of a dry tropical forest.

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