Producing the Proboscis

Butterfly Proboscis

Butterfly Proboscis
Image: Stephen Nagy, Nikon Small World

The proboscis of the butterfly is formed during the pupa stage. The lobes (galea) of the maxillae (middle mouthparts) extend and are formed as two separate half tubes. When the butterfly emerges from its chrysalis, each half of the proboscis is drawn out separately. Each half coils and the coils may become entangled. The butterfly contracts the muscles at the base and the half tubes extend. As the coiling and uncoiling of the mouthparts is repeated, the two halves align to form a single tube starting from the base of the mouthpart. Fluid released from the mouth causes the two halves to more strongly adhere and create a tube through which more liquid can travel down the tube. Ventrally, each half has “hooks” that interlock in a tongue and groove fashion. The dorsal side of the proboscis has plates that overlap.

The tightly opposed halves are then made into a tight coil such that each part of the inner coils is held in place by the coil above and below. The unlinked portions of the tube are coiled and uncoiled until they press together. Anti-paralel movements of the two halves properly align all hooks and plates. The proper alignment of the mouthpart halves takes between 30 minutes and 4 hours. After the cuticle hardens, the mouthparts cannot be easily separated. They are hardened in place. If linkage has not occurred before the cuticle hardens, the halves cannot be linked nor can a proboscis that is forced apart re-link properly. It is an odd way to make a feeding tube, but it works for butterflies.

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in behavior, Biomaterials, by jjneal, Taxonomy. Bookmark the permalink.

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