Our native forests – ngahere – have complex ecosystems. Within the wider ecosystems are smaller ecosystems, such as the one formed around honeydew. Honeydew is a sweet, sticky substance produced by small scale insects and it forms the base of a complex food web that supports fungi, insects and birds like the kākā and tūī.
University of Auckland Associate Professor Jacqueline Beggs (Ngāti Awa) is involved in native forest restoration. She has a special interest in the role of insects in ecosystems. Jacqueline says that insects are a “hidden story” in the bush because they and their work are often not noticed. Insects cycle nutrients, aid soil formation, pollinate plants and provide food for lots of other creatures.
One group of insects that hold particular interest for Jacqueline are scale insects. There are nine species endemic to New Zealand. Scale insects are tiny and have a simple body structure. They are often described as a bag with a mouth and a very long anal (bum) tube or filament. Scale insects tap into the phloem (sap) of trees such as kānuka and beech and suck out the sugary sap. They use some of the sugar for their own needs and excrete the excess sugar through the thin, waxy filaments.
Nature of science
Mātauranga Māori recognises that Māori have a close association with te ngahere – the forest – and are keen observers of forest interactions. Such observation and the systematic collection of data is a cornerstone of science research.
Honeydew – a keystone resource
The sugary droplets are food for all sorts of organisms. Birds and insects eat the droplets as they are excreted. Black sooty mould grows where droplets splash onto tree trunks, forming small ecosystems of their own. When honeydew falls to the ground or rain washes it into the soil, the extra nutrients influence decomposition and nutrient cycling in the forest soils.
Te take – the problem
While it is well known that native birds and plants are under threat from introduced species, it is less common for people to think about the risks to our native insects. Foreign wasp species eat honeydew – but instead of just sipping the droplets, they consume the filament tube, killing the scale insect. Wasps are responsible for up to a 90% reduction in the amount of available honeydew in some forests. This food loss affects the whole ecosystem – birds, beetles, moths, sooty moulds, decomposition, nutrient cycling and more.
Te whāinga – the aim
A lot of effort has gone into forest restoration using knowledge of plant succession and how to bring back native birds. Jacqueline’s research is helping to enhance the process.
Scale insects are poor dispersers – they don’t spread easily. Jacqueline says, “If we are going to restore forest ecosystems, we need to restore the insects and all the functioning that they bring to the systems.” If introduced early in the restoration process, the insects will activate key interactions in the food and nutrient cycles.
Successful restoration also relies on predator control. In 2015, the Department of Conservation (DOC) conducted a pilot programme at five South Island sites. Protein baits – unattractive to bees – effectively reduced wasp activity in monitored nests by more than 95%. DOC will continue its work with scientists and key stakeholders in looking for a long-term solution to wasp control.
Scale insects and the honeydew ecosystem
Scale insects are tiny in size but have a significant impact on the forest ecosystem. Find out more about these important invertebrates by watching the video above and also Scale insect lifecycle. The role of honeydew, a keystone resource, is explained in the article Honeydew ecosystem and the video Honeydew.
In this activity, students construct a food web using string and pictures. Their web will show the network of species in the honeydew ecosystem.
Constructing food webs
Introduced wasp species pose a real problem for New Zealand biodiversity. The article Action needed on NZ’s wasp problem provides information on how German and common wasps arrived in New Zealand and some of the risks they pose. Angry wasp versus hungry ant tells a fascinating story about wasp behaviour and could explain why they are so widespread and invasive.
Not all wasps are the bad guys. New Zealand has native wasps that help control pest caterpillars. Read about these small, short and stout insects in Middle Earth wasps.
Landcare Research’s Wasp Web has information on introduced Vespula wasp species – their life cycles, distribution, control, first aid advice and much more.
Read about the Department of Conservation’s wasp control pilot programme.
Visit Pond to view Te aitanga pepeke – the insect world with links to resources and community activities.
Western science provides one pathway to the solutions required, but we must uncover and integrate the knowledge from our past so that mātauranga Māori can take its place in restoring the realm of Tāne to the natural balance it once knew.
Dr Ocean Mercier
Watch Series 2/Episode 3: Honeydew: The Food of the Ngahere
Project Mātauranga is a television series that investigates Māori world views and methodologies within the scientific community and looks at their practical application. Each of the 13 episodes in series 2 shows how western science and Māori knowledge systems are combining to provide solutions to a variety of challenges.
The Science Learning Hub thanks Scottie Productions for allowing us to host these videos.