My Caterpillar looks sick,
and has fallen off its twig.
What is wrong with it?
Don Herbison-Evans,
Stella Crossley

sick Coscinocera hercules caterpillar
(Photo: courtesy of Eve Stafford)

  • Maybe it is dessiccation. Some caterpilars are well known for liking their drinks. Try offering it some wet leaves.

  • There are bugs that infect caterpillars. One is the bacterium Bacillus thuringiensis. This bacterium is susceptible to antibiotics, so you could request some Penicillin for it at your local Vetinary Clinic. But if the bacteria have produced a lot of toxin already, you may be too late to save your caterpillar.

  • Or it could be the fungal disease Ophiocordyceps sinensis. Again, you could ask your local Vetinary Clinic to treat it with anti-fungal drugs such as Amphotericin or Voriconazole, but again you may be too late, and the fungus may have released too much toxin already to save your caterpillar.

    dead caterpillar with fruiting body of the fungus Ophiocordyceps sinensis growing out of its head
    (Photo: courtesy of Nicolas Merky)

  • Or it could have a parasitic wasp or fly infection. The larvae of the wasps or flies live inside the caterpillar, and eat it away from the inside. We do not know any way of curing this infection.

    dying Brunia replana, caterpillar with cocoons of a number of wasp parasites.

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    (written 27 April 2014, updated 28 May 2017)