This is the larvae of course
The fly is just a good sized ugly fly. Everyone said the eggs are transferred by mosquitoes but I see no reason why the fly itself couldn't inject the egg. I got mine in Belize and hear they drive all the grazing animals crazy. I don't doubt it at all as I went through the 6-8 week growth period with one in my scalp.
Went to one doctor in Seattle and he said it's just a little red. Went back and he said it's just a little bump. Went back again and my doctor had moved to another clinic. Another doctor and we started over. Neither had any idea and didn't ask about my travels. When the larvae get bigger they feel like someone is sticking pins in your skin .... usually at night making it hard to sleep. After 2 days with a hot towel it finally popped out. I took it to Swedish hospital emergency and they had no clue. Mine was gray and not brown like above. That experience was unpleasant enough to make me hesitate to return to southern Mexico.
Botflies are obligate parasites of vertebrates: their larvae must undergo development inside a warm-blooded host. Epidemiology and Ecology: The distribution of Dermatobia hominis botfly includes Mexico, Central and South America. In the U.S., cases usually occur in travelers who have visited endemic areas