So when I was a kid in Gulf Breeze, FL there used to be a truck that drove through the neighborhood spraying for mosquitos.
There is one in Utila and he just drove through. A huge fog of bug poison is wafting from the road to the apartment.
And yes it smells like bug spray.
For those of you that have never seen one, here is a video of one in Mississippi. It sounds just like that, although I did not get a look at it.