Holly
Blue (Celastrina argiolus)
C. argiolus is primarily found in
the southern half of the British Isles and is a frequent visitor to gardens, churchyards and parks.
This species is renowned for fluctuating in numbers, forming a predictable
cycle over several seasons, thought to be caused by the abundance of the parasitic wasp
Listrodomus nycthemerus whose sole host is the Holly Blue. The wasp lays
its eggs in the larvae of C. argiolous,
with a single adult wasp eventually emerging from the pupa. In
England and Wales this species is widespread and common, south of a line
running from Cumberland in the west to County Durham in the east. It is also
found on the Isle of Man and throughout Ireland, but is absent from Scotland
except as a scarce vagrant.
There
are two broods each year, although there may be only one brood in the north.
Adults from overwintering pupae emerge as early as the first week of April in a
typical season, with the next generation emerging during mid July and early
August. The three images above are of summer brood individuals. The first two pictures depict the same male. The third image is a female nectaring on bramble blossom.
