The name says it all...
"We love to hover..
Tiny-Winny, we fly fast
with our buzz in air,
We are two-winged masters
We are the flies ...!
Call us hover flies or flower flies...
You will find on every flower..!
We are the hover-flies!"
~ Amtrips
More info: http://en.wikipedia.org/wiki/Hoverfly
http://crawford.tardigrade.net/bugs/BugofMonth14.html
