[Syrphidae] Hoverfly behavior

[Jules Fraytet]

Greetings to the Hoverfly discussion list

Would someone be able to comment on the following hoverfly behavior?

I was at the Carolina Sandhills National Wildlife Refuge,Chesterfield 
County, South Carolina recently and watched  briefly as a Steel-Blue Cricket 
Hunter wasp (Chlorion aerarium) dig a hole in the sand probably for dragging 
it's prey into this hole and to lay an egg on the prey.    I did not witness 
that process, but I did see two Syrphidae, perhaps Eristalis, hovering as if 
watching this digging activity.

One landed on a nearby (approx  25 cm  away ) grass leaf and stayed there 
perhaps 3 or more minutes.   The other landed more intermittently on another 
close herbaceous plant.   What would the hoverflies be looking for since 
they feed on nectar and pollen?

Thank you very much

Jules Fraytet