So annoys me why folks want to gratuitously kill insects and their ('babies') larvae. I note a thread about Drone flies posted a year ago. I have added an answer but now open a present advised new thread on the issue.
Drone flies are of the Hover fly species which are totally harmless to us stupid Homo sapiens which at the sight of a bug 'scream and shout' and reach for the poisons of fly sprays and other zapping toxins. Hover flies predate other 'nuisance insects' and also provide the vital job as pollinators as well as being themselves food for garden birds. I also have a water butt full of these intriguing, if ugly, larvae, which appear to knot themselves together by their wiggly tails. I swirled a twig amongst them and they untangled. Except, next day they are all tangled up again. I shall be happy to leave them with the thought that glorious striped, buzzing Hover flies will metamorphose from ugly maggoty larvae creatures with long wiggly tails into pretty flies which will prance about my flowers and fill lazy summer days with their sonorous buzzing and delightful hovering antics. www.naturespot.org.uk/species/common-drone-fly