Merodon equestris
"J.Mäsgen" (Fri, 16 Nov 2012 08:29:33 PST)

Shading prevents bulbs beeing infested with bulbfly, the greater and the
lesser!
Here in Germany light shading should used from April on until the end of
the dormant period. Bulb flys only lay their eggs at places with full
sun to be sure that their is enough summer heat for the development of
their larvae in the ground.
If you have bulbs planted out in the garden I have best results were
deciduous trees and shrubs form naturally some shade in april.

Micael