My anecdotal experience.

I was in SERE school, in the US Navy.

We were in the field portion of the training, the low mountains of SoCal.

I would periodically get this weird, almost bitter smell. Fast forward a day and I realized the smell was when there was an ant on me.

I don’t know if it was a combo of the environment, the type of ant, the lack of food or showering for a few days, but it was pretty reliable.

After SERE was over, I have never experienced it again.