Mollusk mystery solved
They are small in statue but their sudden appearance raised some big questions which have finally be answered.
Blenheim man David Olliver was left puzzled by thousands of empty snail shells which appeared on his path and driveway every time it rained.
The eccentric grass snails ( Vallonia excentrica) were discovered laying empty and crunched underfoot every time David and his wife, Pat, left their house.
Now an academic from the Museum of New Zealand Te Papa Tongarewa has revealed the snail shells were washed there by the rain and wind. Collection manager sciences and malacologist Dr Bruce Marshall says the snails are found in huge numbers.
‘‘ Vallonia excentrica live in pastures and can occur at high densities of up to 1500 per square metre.
‘‘It lives for only a few months, and has two generations per year.
‘‘As a consequence there may be large numbers of empty shells in a small area of grass. The empty shells on the path presumably floated there from the adjacent grass.’’
Vallonia excentrica is a species of very small air-breathing land snail which was introduced to New Zealand from the Mediterranean and Western Europe.
They grow to between 1.2 and 2.3 millimetres in size and are difficult to see with the naked eye.
David says he only found the snails after hearing the noise the empty shells made when they were walked on.
‘‘It’s marvellous to finally have some answers,’’ he said.