The area around Volgograd is known for its swamps and wide rivers, the perfect breeding ground for insects during the hot and dry summer in the Russian south.
Russian media said authorities used planes in the months before the game to spray the area around the stadium, which is next to the massive Volga river, with a special substance designed to kill them off, but the effort was only partially successful.
Authorities also tried to regulate the flow of water at a nearby hydro-electric dam which locals believe has a direct effect on the number of insects.
Several players were sprayed by staff just before kick-off on Monday, but that didn't appear to be enough either.
England's Raheem Sterling looked particularly bothered by the tiny gnats circling his face before the start of the second half.
Tunisia's Ferjani Sassi was also pestered by them before the took a penalty - but still managed to score as the African side went into halftime level at 1-1 with England.
England went on to win the match 2-1.