Caligo memnon caterpillar osmeterium-like organ

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    • Caligo memnon caterpillar osmeterium-like organ

      Hello Everyone,

      today I found this weird thing on my Caligo memnon L4 caterpillars. When I touch them they lift their head up and project a small "inflatable" horn-like organ. It is similar to an osmeterium in papilionid caterpillars, but there is no smell. I also found the small slit on my L3 caterpillars, but there isn't any horn-like organ. Could anyone explain what this is?


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    • I've got the answer on another platform from Felipe Gil-T.:
      "The prothoracic gland (eversible ventral gland ahead of the first pair of thoracic legs) of the larva of Caligo memnon is used mainly to spray approaching ants to it. This gland contain chemical compounds synthesized by the larva specifically for its chemical defense against predators or enemies."
    • I used GC-MS on this organ for my research in Norwhich Research Park, on caterpillars of the related butterfly Eryphanis sp.
      I found no significant compounds, strangely, except for palmitic acid. But that is a very common compound, I wonder if it is from the protrusion itself or contamination of the samples..
      However, it has been proven that some beetle larvae use palmitic acid against ants, it is found in the fecal shields of the Chrysomelidae larvae.

      There is a smell by the way but it is not very strong, it smells "dusty", like a dusty office..
      More research is needed I think. I've been told the hydrolyzation of the palmitinic acid is also important to look at, but that is beyond my current level of understanding of chemistry. Maybe I will continue if I am better educated in this subject..
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      The post was edited 1 time, last by Bartmantis ().