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The Amazing Butterfly Proboscis

I have long wanted to make a post showcasing the incredible maneuverability and complexity of the butterfly proboscis – something often overlooked by casual observers. The proboscis, or the elongated mouthpart of the butterfly, is often likened to a straw but in reality, it is much more complex than that.

During the pupal stage, the proboscis is formed in two parts, and each C-shaped half is known as a galeae. Once the butterfly emerges, it must then “assemble” its proboscis by “zipping” the two halves together to form the hollow feeding tube we know as the proboscis. Amazingly, each galeae is capable of moving somewhat independently, having its own blood supply, muscles, nerves and even a trachea! Once united, however, the two halves move cohesively. Recent research has shown that the saliva of the butterfly is responsible for uniting the two galeae together to form the proboscis via capillary action (Chengqi et al. 2018). In addition, there are tiny projections called legulae on the ventral aspect of the proboscis that link together once the two halves are assembled (Chengqui et al. 2018).

An added benefit to having the proboscis in two pieces is that it comes apart for easy cleaning, should an obstruction form. This can be especially important for the Nymphalids (Brushfoots), many of which feed off fermented fruit, carrion, dung and other organic matter, as well as the Heliconids (Longwing Butterflies) who are unique in their ability to process pollen. Pollen allows Heliconids access to amino acids otherwise lacking in nectar, which aids in reproduction and helps to extend their lifespan.

Currently, scientists are studying the butterfly and moth proboscis for its amazing properties in hopes of developing a micro-siphon with far-reaching implications in the medical field.

Video: watch a monarch emerge and witness the proboscis come out in two parts!


Zhang Chengqi, Adler Peter H, Monaenkova Daria, Addrukh Taras, Pometto Sullen, Beard Charles E. and Korner Konstantin. Self-assembly of the butterfly proboscis: the role of capillary forces. J.R. Soc. Interface. 2018. August 21, 2022. 15:20180229.

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