Identification needed - what type of pond skaters

Identification needed - what type of pond skaters

Observation - Identification needed - what type of pond skaters. Description: Pond filled 3 months ago - Pond skaters arrived 2 days later - now there are 20 or 30 skimming around - but what type?

Pond filled 3 months ago - Pond skaters arrived 2 days later - now there are 20 or 30 skimming around - but what type?