Wonder web of nature holds key to rare butterfly

It's autumn again and nature detectives are hot on the case of an elusive wonder web.

If you want to join in the search while enjoying a walk across our upland heaths or grasslands in the Belfast Hills, then keep an eye out for webbing on top of low vegetation, especially with caterpillars resting on top.

It may be the very rare marsh fritillary butterfly, one which naturalists have been looking out for over the last few years.

They have a curious habit of sunning themselves in good autumnal days which makes them easily visible for a short period. Pinpointing a web in autumn is invaluable to conservationists to help locate a colony of this very rare native butterfly, so make a careful note of the location or even take a picture of the web and surrounding site. Then get in touch with the Belfast Hills Partnership offices.

The marsh fritillary butterfly was once widespread throughout Britain and Ireland, but over the last 100 years its numbers have severely declined and it is now under threat of becoming totally extinct. For this reason, and the fact that this was once one of its European strongholds, remaining populations have been declared important from a European perspective.

It has been reported to be present in the Belfast Hills up to the 1990s but has not been seen since.  The marsh fritillary is a Northern Ireland Priority Species for conservation and a Species Action Plan has been produced to ensure its future conservation.

"It seems to be a very fussy creature, hence its worrying decline," said Partnership Manager Jim Bradley.

"It needs plenty of its food plant, Devil's-bit scabious, but also needs other flowers to gather nectar from and just the right sort of grazing and management. It never travels too far so when it does die out it seems to take many years for it to come back to an old haunt. It also has a talent for hiding which means just when it's thought to be extinct in a locality its population increases again. Nevertheless, new sites can and have been found in Northern Ireland recently so there is still hope that somewhere in the hills is a colony hanging on for better times."

If you see some marsh fritillary or any other butterflies or other wildlife of note, please get in touch.

Factfile

-The female lays batches of eggs on the underside of Devil's-bit Scabious leaves in June.

-During the autumn the brown-black, spiny caterpillars feed together on Scabious leaves inside a silken white web.

-During the winter they hibernate together in a small web, hidden in the sward. The caterpillars emerge in February or early March and separate; sometimes wandering to find fresh Scabious leaves. By late April-early May the caterpillars change in to a chrysalis and emerge as adult butterflies 2-3 weeks later.

The Belfast Hills Partnership has species recording cards with more information on the marsh fritillary and its caterpillars. Just contact the offices to request one.