Hello and thanks for investigating this important health question!
"Warbles" is a common name given to the larvae of flies that lay an egg on a weak animal (usually very young, or sickly). These are also known as Bot Fly larvae, or Cuterebra after the scientific name.
The larva develops under the skin and is noticed as a lump with a hole in the middle...the parasite pops its face up and down out of the hole to breath.
These pests should be surgically removed by a licensed veterinarian as soon as possible.
Here is a link to a web site with a kind of graphic photo, but good information about these insects:
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