This picture was taken when I was trying to click a spider in its web .I found these insects moving in pairs hanging from the web and gliding around it without getting entangled.It appeared as if they were performing a synchronised dance .Later, I learned that these are Gall Midges (Cecidomyiidae).This trapeze act is apparently a widespread phenomenon in the Cecidomyiidae, especially in the subfamilies Porricondylinae and Cecidomyiinae. The behavior was first reported (published) in 1853 by Johannes Winnertz.
Spider webs are used as roosting places for a certain species of gall midge, family Cecidomyiidae. When most flies become tangled in spider webs and eventually a become meal for the spider, these tiny flies are able to select the non-sticky foundation threads of spider webs and safely suspend themselves from them. Predators of these flies would risk of being entangled in the spider web .
Really fascinating to know that such small insects have adapted themselves to thrive on something like spider web which is a death trap for so many other larger insects.