The dainty damselfly, a smaller relative of dragonflies, was washed away from its single East Anglian pond in the severe coastal floods of 1952/3.
Now, a few individuals have been found at a site in north Kent.
Conservationists believe the insects were blown on the wind from France or Belgium where they have become more common, probably due to climate change.
They were found earlier in the summer by Gill and John Brooks, who record sightings in Kent for the British Dragonfly Society (BDS).
“It’s most likely that they’ve come in from the continent,” said Dave Smallshire, convenor of the BDS Dragonfly Conservation Group.
“The spread northwards across the continent seems to be associated with climate change.
“And it’s quite likely that they’ve caught a lift on a southerly breeze and popped across the English Channel.”
The species recently established itself again in Belgium after a long absence, and has been documented for the first time in The Netherlands. Last year, specimens were found in Jersey.
Damselflies are very similar to the more familiar dragonflies, but are usually a bit smaller, and weaker fliers.
When resting, they usually have their wings folded along their backs, whereas dragonflies tend to keep theirs at right-angles to the body.
There are 17 species that breed in the UK.
One, the small red-eyed damselfly, first appeared in 1999 – also thought to be a consequence of rising temperatures – and now breeds across tracts of south-east England.
Whether the dainty damselfly can form stable breeding population is not yet clear.
“What we need to do is follow up this year’s observations with some more intensive survey work next year,” said Dr Smallshire.
“They may be able to breed from egg through to adult in one year.
“So next year we would be looking for the exuvia – the discarded larval casing – and that would be evidence that they have bred successfully in Britain.”