Odonata: Coenagrionidae
Ischnura heterosticta
Many Damselflies are so tiny and just look like a black line on a lily pad until they suddenly fly away and you realise you were looking right at them. The females in particular are much sometimes plainer and the species hard to work out.
Identifying this female Common Bluetail Damselfly was helped by seeing the two brownish spots, one behind each eye. The male has a blue spot behind each eye.