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Published: 2007-04-12 00:00:00

It’s small. Very small. But a new species of insect that has been discovered in Hamilton is a big deal for scientists at Environment Waikato and NIWA.

Two male insects belonging to the caddisfly group have been found as part of a joint study by the two agencies into what kind of life exists in Hamilton’s urban stream environments.

Caddisflies are small, moth-like insects that live in wet habitats such as streams, rivers, ponds, lakes and areas of natural seepage.

The pinhead-sized animals found in Hamilton weigh about 0.09 milligrams and their wings are less than two millimetres long.

“As far as we know, no one else has found this species anywhere else in the world,” said Environment Waikato freshwater ecologist Kevin Collier.

“It’s unusual to find a new species full stop, but it’s even more unusual to find it in a city. Cities are very altered environments and all sorts of things flow into urban streams. This doesn’t make life easy for insects like the caddisfly, which is generally associated with clean water.”

Dr Collier said all insects contributed to biodiversity values, no matter how small they were, and the caddisflies could be an important food source for other animals.

The two caught in Hamilton flew into an ultraviolet light trap positioned in a wetland area next to a tributary of the Kirikiriroa Stream in Mangaiti Park, in the north of the city.

“This riparian wetland isn’t directly affected by the stream, which allows it to maintain its natural hydrology and water quality to a degree,” Dr Collier said.

“The caddisfly discovery is really exciting for us because it shows some places in Hamilton are capable of supporting unusual species which form part of diverse ecological communities – even though they are part of a highly modified urban landscape – as long as the right sort of habitat remains intact.”

NIWA scientist Brian Smith, one of New Zealand’s leading caddisfly experts, was able to tell the new species apart from more than 250 known to exist by studying its genitalia.

“Caddisfly genitals are like lock and key mechanisms – a key won’t fit in a different lock – meaning males of one species can only mate with females of the same species,” Mr Smith said.

“I guess you could say shape matters more than size when it comes to caddisflies.”

After comparing the Hamilton caddisfly with examples of other species sent down from Auckland Museum last week, he is firmly convinced it is a new species, rather than a variation on an existing species.

The next step is to name the insect and publish a formal taxonomic description of it in a scientific journal, explaining how this species differs from those already known.

“The name I’m proposing is Oxyethira kirikiriroa, which seems fitting because kirikiriroa is the Maori word for Hamilton,” Mr Smith said.

“Once described formally it will be recognised internationally.”

Mr Smith has had two species of caddisfly – Triplectides smithi and Edpercivalia smithi – named after him through helping with other scientific studies.

Dr Collier said Environment Waikato was just beginning to understand the value of seepages (wetland areas) in urban settings.

“The first step is finding out what kind of animal life exists in our city streams, which is what the joint Environment Waikato and NIWA project is all about. Once we know what’s there we can begin to look at ways of managing and protecting what we’ve found.”

He commended Hamilton City Council, which has undertaken a native tree planting programme in Mangaiti Park in a move to improve biodiversity.

“This gives us confidence in the security of the caddisflies’ habitat in future,” he said.

Environment Waikato and Hamilton City Council are working together to promote and protect the biodiversity values of city streams.

Hamilton residents can do their bit by washing their car on the grass and disposing of wastes in environmentally friendly ways, rather than tipping them down storm water drains.

Resisting the urge to drain and concrete wet areas in gully sections is another way to help.

“Wet areas are inconvenient because you get your feet wet, but they could be home to rare creatures like this caddisfly,” Dr Collier said.

“Small streams and seepage areas that aren’t connected to storm water are probably among the most ecologically valuable aquatic habitats in the city.”