Dragonflies released to kill sandfly

Press, 23 October 1984, Page 16

Dragonflies released to kill sandfly

By OLIVER RIDDELL It is now more than 50 years since New Zealand newspapers carried the headlines, “Natural enemy liberated” and “War on sapdflies.” These announced the arrival of a new resident in New Zealand, the humble dragonfly. Professor Edward Percival, of Christchurch, liberated the dragonflies, acting for the D.5.1.R., the site of the historic event being Cass. It had been decided to do something about the sandflies which infested the inland areas of the South Island. It was said, cautiously, at the time, “It will probably be some time before it is known whether the liberations have been a success.” Only those familiar

with Cass, and similar areas, 50 years later, can judge that. Anyone from the viewpoint of the 1980 s who is horrified at the potential ecological disaster inherent in liberating an introduced species to control an indigenous “pest” might pause when reflecting on the alternatives considered. The only reason, dragonflies were chosen was because the breeding places of sandflies, which spend most of their lives in an aquatic stage ; ip fast-flowing streams, were considered unsuited to wholesale flushing using kerosene of oil—■. acknowledged to be lethal to sandflies in more favourable surroundings. The aquatic stage of certain Species of dragonfly

inhabits the same kind of water, and it was found that where dragonflies lived there were few sandflies. The dragonflies liberated by Professor Percival were of an Australian species, a little smaller than the native New Zealand variety, that lived at higher altitudes. About half the consignment shipped from Australia survived. That was considered a very high proportion, because most of the dragonflies had had to tie obtained during -their aquatic stage and their transport presented difficulties. • ,F . . Consignments of the same species of dragonfly were also liberated in the Nelson area, and later at .. Cass again. ■ *