The red “fence” shows a border that mosquitoes can’t pass through, but it is safe for everything else. There is no top coverage because mosquitoes don’t fly very high.
When was the article written? I can remember approximately 6 years ago reading an article on the front page of The Straits Times regarding mosquitoes, Dengue Fever and Malaria. It was a scientific sturdy of many years I can remember the section where it stated that common understanding that mosquitoes do not fly more than a few feet above the ground. At that time Singapore were experiencing a few deaths from Dengue fever, not sure of the number of malaria cases, and they could not determine the reason for this as there is no breeding ground for mosquitoes at groud level. They eventually found that the mosquitoes were breeding in water trapped in the gutters of high rise buildings.