Similar to regular mosquitoes, however these ones have a name that rhymes which increases their general douchebaggery. They are typically seen sucking blood, lifting weights, tanning, and getting mad mosquito pussy.
In typical use this is just a term that is just exclaimed with no context.
Buddy #1: Bro I'm so sick of these Guito Mosquito problems
Buddy #2: The fuck? What does that even mean?
Buddy#1: I dunno.