Investigate a hidden world of critters. Learn how macroinvertebrates are indicators of water quality at the Open Lab.

A macroinvertebrate is a living organism that can be seen by the naked eye (macro), and doesn’t have a backbone (invertebrate). The presence or absence of these macroinvertebrates in freshwater ecosystems give us a good indication of water quality.

Click on image to enlarge

This Stonefly nymph, found in the Kawharawhara Steam within the bounds of Otari-Wilton’s Bush is missing it’s second cerci (tail) and has gills between.

Some macroinvertebrates are very tolerant of pollutants, while others are extremely sensitive. Therefore macroinvertebrates such as mayflies, stoneflies and caddisfly nymphs can be used as biotic (living) indicators for stream health. An index,  called the Macroinvertebrate Community Index (MCI), has been developed for this purpose.

In a healthy stream, it is best to find a diverse range of macroinvertebrates with a high numerical value. Mayfly larvae (pictured below) and stonefly larvae (pictured above) are very sensitive to pollution with a high number they are what we hope to find in a stream to indicate a good water quality.  Please view “A user guide for Macroinvertebrate Community Index”  to gain an in depth understanding of the MCI and its applications.

click on image to enlarge
Click on image to enlarge.

These two photos are both of mayfly nymphs taken during the pop up Open Lab session at Zealandia.  Notice their cerci (tails) count three.  There are four types of nymphs we can classify them by how they mobilize themselves.  The first photos is of a crawler and the second a swimmer.



These little guys were photographed at the pop up Open Lab session in Otari-Wilton’s Bush.

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Scientific name: phylum Arthropoda, class Diplopoda. From Greek “diplos”, two, and “poda”, legs, referring to two legs per segment.

Common name: millipedes.

Maori name: weri mano

Visit Massey University website to view their Guide to New Zealand Soil Invertebrates.

If you cant wait till the next Open Lab session to view more invertebrates try your hand at collecting them yourselves and view under a handheld magnifying glass.  You can simply scoop up a tray fill of leaf litter and a bit of soil (discard large leaves and twigs to make sorting easier).  Spread out  your soil and leaf litter sample in a thin layer in a shallow pan and try and identify what you find.

Or you can trap them using either of the methods DOC suggests in their article “Take a garden insect census“.

If you have trouble identifying your find or simply want to share you critter photograph it and upload it to NatureWatch.

Pop Up OPEN LAB at Otari-Wilton’s Bush


The Open Lab popped up at Otari-Wilton’s Bush  on Sunday in the newly refurbished Cockayne House.   Karin Mahlfeld and Natasha Evans, the Open Lab founders, played host to a diverse group of invertebrate enthusiasts of all ages.

Children alongside equally curious parents sifted through leaf litter collected with the help of Dave Roscoe from within the bounds of the park.  Petri dishes were filled with debris and an assortment of visible mini beasts were examined under the microscopes.   Some critters previously overlooked due to their minute size scuttled into view.

Bronze beetles, mites, common earth worms, and micro snails were identified.     One young girl who was very taken with her discovery of a micro snail is sure to be following Karin’s footsteps in no time!

Those not engaged with the leaf litter scooped freshwater invertebrates into petri dishes and ice cube trays.  Stoneflies were the most numerous as well as Caddishflies in the freshwater sample taken form Kaiwharawhara Stream near the Troup Lawn. One boy, so excited about what he was discovering announced with pride each time he scooped up a different species.   He even managed to look at the spent exoskeleton of a few mayfly.   From our lay observations of the types of macro invertebrates present the stream appears to be in reasonable health. For more information on using macro invertebrates to assess stream health visit this site.

The Open Lab is pleased to be able to cater to a group that ranged from children as young as three to those continuing their research in retirement.   Stimulating interest and awareness in biodiversity and invertebrates in particular is what Open Lab is all about.

Karin later gave a short presentation on Micro Snails.   Karin’s personal collection of pinned micro snails were popular and Dave’s photography displayed on posters made them larger than life.  People were encouraged to pick up and examine the diverse range of species including macro snails such as the Wainuia.

Click here to have a listen to this interview “An Extraordinary Diversity of Land Snails” on Radionz to hear more about the unsung micro snails!

Many thanks to David Roscoe, Margaret Crimp and Andrew Evans for your time during the session.   We’d also like to thank The Clinic – Ngaio School’s community learning space for the loan of their equipment.   And of course to Otari- Wilton’s Bush and Wellington City Council for providing a space to pop up in!

This is the second time the Open Lab has run.  We’ll be returning to Zealandia during the school holidays and plan to be at the zoo late November.  On the 8th of November we’ll be popping up at the Pest Fest!

Story by Natasha Evans

The early days…

The Open Lab showcases unusual creatures

Do you ever wonder what creatures live beneath the leaf litter or what micro-organisms are swimming in your stream? Well, now you can find out at the Open Lab.

The Open Lab is a pop-up laboratory that allows the public to examine live specimens under microscopic lenses. Both children and adults rummaged through soil and leaf litter to find live invertebrates. Once the participants found an organism, they viewed it under a microscope and identified the organism with the help of scientists

“It’s a great learning experience for everyone. The children are quick to learn how to use the microscope,” said DOC Science and Capability Honorary Ranger Dr. Karin Mahlfeld.

Run by a few of DOC’s Science and Capability Volunteers, the Open Lab is a mobile laboratory that is free for the public. A portion of the equipment, including microscopes and laptops, were kindly loaned to the Open Lab from The Clinic, a community-led learning initiative at Ngaio School. The Open Lab aims to increase general awareness of invertebrates and provide an educational opportunity for the public.

The Open Lab made one of its first appearances at Zealandia on Saturday 18 July. Over 50 participants showed up to utilize the lab’s equipment.

“The children are really fascinated to see what’s out there on a microscopic level,” said Zealandia Education Ranger Sue Lum. “The Open Lab’s hands-on approach captures the wonder of the kids’ interest and imagination.”

Given the wet weather during the Open Lab at Zealandia, this was a perfect opportunity for families to get their hands their dirty while staying dry.

“The Open Lab brings the outdoors in! It’s a great activity when it’s raining,” said Kate Studd, chemical engineer and mother of two.

Mayflies were the most common invertebrates identified at the Open Lab at Zealandia. Scientists were particularly excited to find a leaf-veined slug, which is a member of an ancient family of terrestrial molluscs. This particular species is commonly found around the Wellington region and looks just like a gherkin.

You can join the fun at the next Open Lab, which will be held at the Cockayne Centre at Otari-Wilton’s Bush on Sunday 23 August from 2-4pm.

Story by Amy Brasch