Brenton Blue Butterfly
(Picture Natures Valley Trust)
The Brenton Blue butterfly was rediscovered in Nature's Valley in 1977 a 119
years after first being discovered in the Knysna district.
A research
programme at Nature's Valley has been initiated by the Nature's Valley Trust.
The objectives of the research are to find methods to promote the growth of a
large population of O. niobe's host plant at the Fynbos Reserve in Nature's
Valley, where O. niobe used to fly. Part of the reserve has been burnt and
cutting is taking place in the unburnt portion. The research is being conducted
by the botany department of Rhodes University.
The establishment
of a fynbos reserve in Nature's Valley primarily to create a habitat for the Brenton Blue Butterfly
can be seen as a sterling effort in the preservation of the Brenton Blue
butterfly.
This butterfly's survival is largely determined by the presence of the host
plant, Indigofera erecta, which the larvae exclusively feed on.
There is reason to believe that a bitter-sweet symbiotic relationship exists
between the Brenton Blue and one of the 28 species of ants found on the reserve.
Being a member of the Lycaenid family of butterflies, they can only complete
their life cycle in association with a particular ant species.
The larvae have special glands that secrete a substance both nutritious and
enjoyable to the ants. The larvae also emit pheromones (scents) which mimic
(copy) ant brood emissions.
These devices induce the ants to treat the larvae as part of their colony and
provide them with protection from cold, fire and predators. Pupation usually
takes place inside the ant nest.
Research by Dave Edge:
Specific habitat
The Brenton Blue Butterfly needs very specific habitat for its survival. It
lives in the coastal fynbos in a high rainfall area on a southern facing slope
near the sea. The butterfly caterpillars feed only on one plant - the Indigofera
Erecta - that has a tiny salmon-pink flower.
Adult butterflies hatch out twice a year, in November and February and live for
only 2-3 weeks. During 2003, the February brood yielded four times as many
butterflies as the November 2002 brood, and four times as many eggs were laid.
It is believed this was the result of vegetation management techniques that were
implemented.
"I burned a section of the vegetation, but discovered quite by accident, that by
cutting a path through the thick bracken, the host plant multiplied four times
more than with the burning technique," Edge says.
Ants
An important observation has been the interaction between the butterfly larvae
and nocturnal Camponotus Baynei ants.
"We were never quite sure what role the ant played," says Edge. "I set up an
observation unit at home and discovered the caterpillar eats the roots of the
food plant, but the ants dig holes that allow the caterpillar to get to the
roots. In return they are rewarded with a secretion from on a honey gland on the
caterpillar’s rear."
For the time being the future of one of the world's rarest butterflies appears
secure.
"At the moment things look good," Edge says. "The population is steadily
increasing."