- Marbled White -

David Harper and David Streeter, BIOLS

In July he prepares to fly,
In August go he must,
And no one can remember,
A Cuckoo in September.

Last week we were reminded of this traditional verse (which has many variants) while we watched a Cuckoo devouring caterpillars from the Blackthorn bushes by the Mantell building.

Since Cuckoos no longer breed nearby, it was probably already en route to Africa. Certainly, most adult Cuckoos - which migrate several weeks ahead of their fostered young - will be south of the Sahara by the end of August.

Our present musings appear on Saint James' Day, 25 July. This was once the annual starting date for a major local industry based on the trapping of tens of thousands of migrating Wheatears by shepherds. These birds were an esteemed delicacy, and so many traps were dug into the turf that some of the fields between campus and the sea appeared to have been ploughed!

Although naturalists have tied themselves in knots over these plump little birds' name, it is simply a corruption of the 'white arse' they reveal in flight. Look out for them in open areas near campus, including the sports fields, from now until October or even later.

Amazingly, some of the Wheatears seen around campus late in the autumn have come all the way from Arctic Canada via Greenland, and still have the journey across the Sahara ahead of them.

Butterflies seem to be firmly on the agenda this summer. Last month we reported on a Clouded Yellow on the clover behind Park Village and last week we spotted a Marbled White in the rough grass behind BIOLS.

Unlike the migrant Clouded Yellow, the Marbled White is a resident species especially characteristic of the chalk downs of southern England, where it can occur in colonies of thousands of individuals.

It suffered a contraction in its range early in the last century, but over the last 30 years has made up the lost ground and it would be nice if this beautiful insect managed to establish a permanent colony on campus. Its favoured habitat is tall, rough grassland on a warm slope with plenty of purple-coloured flowers such as knapweeds and scabious.

Egg laying is a pretty casual business. The female simply scatters them at random while in flight and the young go into hibernation as soon as they hatch. The next spring the mature caterpillars feed at night on a range of grasses, especially Red Fescue.

In spite of its name, the butterfly is not a 'white' but a 'brown', like the familiar Meadow Brown and Gatekeeper, both of which are common on campus in the meadow and along the hedgerows behind East Slope. 'Marbled White', 'Marmoress' and 'Marbled Angus' all refer to the distinctive black and white marbled patterning on its wings.