After the cute duckies of Spring are gone, those pesky Mosquitoes arrive!
The Mosquitoes appeared on Gilligan's Island in episode 48 Don't Bug the Mosquitoes which first aired on December 9, 1965. According to TV.com, "three of the Mosquitoes (Bango, Bongo, and Irving) were played by the three singers known as the Wellingtons, the group that sang the Gilligan's Island theme song in the first season!"
Anyway, the Mosquitoes must have left behind the incredible technology that allowed them to play wireless without amps, microphones, or even electricity when they fled the island. I couldn't find any info about who actually wrote the tunes, so if any Gilliganophiles have any info, please spill!