So what are they?

Greetings from the Low Country where the shadows have stretched out from the mossy palmettos on one of the "longest" days of the year. I have been summoned onto the patio of my cousin's matchbox apartment by the siren-like effect of what I call secadas. They are the insects that drone on - usually late in the day - with their lazy whinning...as if they don't want the sun to rest. And I'm with them. Another day down means another day of vacation (time in the South) gone.
But, carpé the day: I have enjoyed time with family on the beach, consumed several quality Pennsylvania beverages, endured a loss, and had more than my fair-share of fried seafood. My subtle buzz is enhanced by the hum of many A-C units just trying to keep up with the demands of the resident condo-commandos that demand a constant 72F inside their habitats. Hell, I'm outside sweating while I can...loving every bless-ed minute of it.
So am I right about they secadas? Have I misspelled it, or are they called something differently entirely? I know I'll hear from y'all.