2 “tongues”


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    Hey all,

    I meant to ask this ages ago but never got around to it. Just had one hatch today, and immediately after the butterfly emerges, you will notice it is like there is sometimes(???) 2 little coils of "tongue" that wind in and out on and off independantly. This goes on for around a couple of hours, then the separate coils become "joined up into one" as it were… that is about the best explanation I can give. The thing is I dont see this on all of the new butterflies, and it was only because of todays observation that I was reminded of it.

    Has anyone got any info on why this is?



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    Jaqui Excellent! What is described here is just as I see it. Obviously there is info on this website I’m yet to explore. Didnt know about the proboscis coming apart in older butterflies. Ive never seen that.




    Hi Swansong – yes when they emerge their proboscis is in two parts, and they have to work at zipping it together. Interesting eh!

    Courtesy Monarchwatch.org’s website:

    The Proboscis – Structure and Function

    Adult butterflies and most (but not all) moths feed on liquids by extending their proboscis and sucking up the fluids through this structure. The proboscis represents one of the many remarkable changes that occurs during metamorphosis from the larval to the adult stage. Larvae use mandibles to bite, chew and move their food into their oral cavity or mouth. The adults lack mandibles and instead ingest their food through two modified structures known as galeae. In cross section these structures are two half circles which are concave like half noons. The galeae fit together such that the concavities from a central tube or channel. An astonishing feature of this structure is that the two galeae fit together with a tongue and groove set of overlapping plates such that the internal tube functions as a straw. (Imagine cutting a straw lengthwise and then fitting it together again so that it still functioned to draw up liquids). The galeae are hollow yet contain muscles, tracheae, nerves and an open circulatory system.

    Opinions differ as to how the proboscis is extended. The most commonly held view is that hydrostatic (fluid; in this case, blood) pressure is used to extend the proboscis and that muscles are used to move the tip of the proboscis and to retract it. A special pump (cibarial pump) is used to imbibe the liquids. The top of the oral cavity can be drawn upward by a strong set of muscles producing a negative pressure, or sucking action, that draws the fluids upward. Since most butterfly flowers contain small quantities of dilute nectar, capillary action at the tip of the proboscis combined with the pumping action must be very efficient for butterflies to obtain nutrients from flowers. The proboscis also has two major types of sensilla (sensory receptors) that are presumably used to assess the qualities and quantity of the liquids.

    The next time you watch a monarch emerge pay close attention to the mouth parts. Often you will see the two galeae as separate structures which the newly emerged butterfly moves back and forth independently until they come together (see link to photo below). Somehow, as these two halves of the proboscis come together, the tongue and grooves overlap and they are “zippered” together forming the complete tube. Occasionally, in very old butterflies, the galeae become partially unzipped. When this happens, the butterflies have difficulty feeding and die shortly thereafter.


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