Proboscis: Definition, Function, and Examples

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Proboscis Definition

An extended or protruding appendage in the head area of certain animals is referred to as a proboscis. The proboscis is a hollow tubular cephalic appendage seen in invertebrates such as insects, annelids, mollusks, and ribbon worms.


The proboscis of butterflies, in particular, is linked to the oral area. As a result, their proboscis acts as a feeding or sucking organ.

The proboscis of certain vertebrates is not connected to the mouth, but instead forms a fusion of the nose and the upper lip (as in snouts). The elephant trunk and the proboscis monkey’s extended snout are two examples of vertebrate proboscises.


Proboscis Etymology

Proboscis (plural: proboscises or proboscides) is a word formed from the Ancient Greek word “πρoβοσκίς” (probosks). The latter is a composite of the Greek words “προ”- (pro-) and “βόσκω” (bósk, which means “to nourish” or “to feed”).

Proboscis in Invertebrates

In insects, the proboscis is generally a chitinous tube produced by the modified maxillae or labium. The proboscis of annelids and mollusks is generally a protruding part of the pharynx. The proboscis of Nemertea (ribbon worms) is a lengthy internal organ that is not linked to the mouth and is not used for eating, but can emerge from a pore in the head.

Proboscis in Acanthocephala

The acanthocephalans (also known as thorny-headed worms) feature a spine-studded anterior eversible proboscis on their heads. It is used by the organism to adhere to the intestinal wall of its ultimate host.

Lepidoptera Proboscis

Butterflies and moths are examples of Lepidopterans. Many have maxillary galeae, which are converted into a sucking apparatus called proboscis when they reach adulthood. The butterfly in the illustration above has a proboscis that looks like a coiled structure under its head.

The proboscis of a lepidopteran consists of one to five segments and is normally coiled when not in use. When the insect starts to suck up and eat, it uncoils and expands like a “sipping straw.” The butterfly in the image above is sucking nectar from flowers using its proboscis.

Two galeae make up the proboscis. Lepidopteran proboscises have a variety of morphological characteristics that reflect their varied feeding behaviours.

Hawkmoths, for example, have extended proboscises that allow them to enter their proboscises into the long tubular blooms and access the nectar within. The proboscis tip of nectar-feeding lepidopterans is very basic, lacking spines and having few sensilla.

Non-flower-feeding lepidopterans, on the other hand, have piercing proboscises that feed on the liquids of decaying fruits and animal fluids. The tip of their proboscis has “spines” and many sensilla.

Some noctuid moths, for example, have a “spiny” proboscis that allows them to puncture the fruit rind and drink the juice. The Asian vampire moths puncture the skin of their animal prey with their sharp proboscis and sip the blood.

Proboscis in Gastropods

At the Monterey Bay Aquarium, a Kellet’s whelk (Kelletia kelletii) displays its lengthy, prehensile proboscis as it feeds on a dead fish.

Proboscis in Vertebrates

The proboscis in vertebrates refers to the extended nose or snout of some animals. Here are several examples:

1. The male elephant seal’s snout

2. Elephant-drawn waggon

3. The proboscis monkey’s enormous nose

4. Anteater’s snout

5. Tapir’s proboscis

Proboscis Citations
  • The proboscis extension reflex to evaluate learning and memory in honeybees (Apis mellifera): some caveats. Naturwissenschaften . 2012 Sep;99(9):677-86. 
  • The arrhinias: Proboscis lateralis literature review and surgical update. J Craniomaxillofac Surg . 2019 Sep;47(9):1410-1413.
  • Proboscis lateralis. Childs Nerv Syst . 2013 Jun;29(6):885-91.
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