Tracking Disease in New Zealand's Monarch Butterflies
![An caterpillar infected with Nuclear Polyhedrosis Virus]( https://www.wgtn.ac.nz/science/outreach/citizen-science-opportunities/tracking-disease-in-new-zealands-monarch-butterflies/black-death-jpg/ls_medium.jpg)
This page has information and resources for the sampling of disease in monarch butterflies.
What diseases occur in New Zealand monarch butterflies?
There are two main diseases that are sometimes seen here in Aotearoa New Zealand and around the world—Nuclear Polyhedrosis Virus and Ophryocystis elektroscirrha.
Nuclear Polyhedrosis Virus (NPV)
Nuclear Polyhedrosis Virus is sometimes referred to as Black Death. Caterpillars with this infection turn black, oily, and slick before they die and then liquefy. If they pupate, the chrysalis might turn black but you won’t see any wings. A foul smell comes out if the dead caterpillar is ruptured.
Ophryocystis elektroscirrha (OE)
Ophryocystis elektroscirrha causes adult butterflies to have crumpled and deformed wings. These adults are unable to fly and will typically fall to the ground after they emerge from their chrysalis. This disease is caused by a protozoan parasite—single-celled organisms that require a host in which to live and reproduce.
Many adult butterflies have lower levels of OE infection and appear normal. They have no crumpled wings. They emerge and fly but carry spores of the parasite that will infect the next generation of butterflies. Our 2020 citizen science study of OE prevalence across Aotearoa found that 59% of samples examined were infected with OE spores.
There are other diseases and predators of monarch butterflies, including wasps. However, NVP and OE are the most commonly observed diseases.
We’d like you to collect caterpillars with signs of NPV
In 2025, we are interested in studying the rates of NPV infection and its genetics across Aotearoa. You can easily sample a diseased caterpillar by following these steps:
- Enclose the diseased caterpillar and the leaves or branches it is attached to inside a Zip Lock or Glad bag (or small plastic container that can be sealed). Cut the ends of the branches to make them fit in the bag and close the seal.
- Record the date, location of your sample, and any observations. Have you seen any more diseased butterflies? How many of your butterflies looked abnormal?
- Place the sample in an envelope addressed to: Mariana Bulgarella, Monarch Disease Survey, School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140.
- Include your name and email address so we can contact you and share the results of the study.
We will place the samples in a fridge until we isolate the viral DNA and study it. Not much is known of this deadly virus infecting Aotearoa’s butterflies.
If you raise butterflies, additional steps will be needed to get rid of NPV. The best way to kill the virus is to disinfect with a bleach solution (your plants, rearing containers, and any surfaces that came into contact with the diseased caterpillar). Please see the below web resources for thorough explanations.
Video and web resources
Websites with information about NPV:
- https://www.internationalbutterflybreeders.org/nuclear-polyhedrosis-virus/?fbclid=IwY2xjawHn3KNleHRuA2FlbQIxMAABHb5R4XS22Aqi_flZjyNNaW67e-_xeIFtoZjB2U2AZwkg9nDqAy54tV8UWQ_aem_KwdIPTIEB6EahkI2hZLW4g
- https://butterflygrower.com/pages/npv-nuclear-polyhedrosis-virus
To sex a monarch butterfly adult, see:
- https://www.butterflybiology.com/blog/2017/2/10/can-you-tell-the-difference-between-a-male-and-female-butterfly
- https://monarchbutterflygarden.net/female-or-male-monarch-butterfly-pictures/
A great reference on monarch butterflies around the globe, including information on OE infection rates: https://www.frontiersin.org/articles/10.3389/fevo.2019.00362/full
The results of our 2020 citizen science project on OE prevalence in Aotearoa monarchs can be found here:
- A citizen science project reveals contrasting latitudinal gradients of wing deformity and parasite infection of monarch butterflies in New Zealand: https://resjournals.onlinelibrary.wiley.com/doi/10.1111/een.13057
- Wing deformities in monarch butterflies in New Zealand: The role of a parasite and the climate: https://kids.frontiersin.org/articles/10.3389/frym.2022.729916/full
There are also some great resources and information at the Moths and Butterflies of New Zealand Trust, at: https://www.monarch.org.nz
Contact details: Mariana Bulgarella (mariana.bulgarella@vuw.ac.nz) and Phil Lester (phil.lester@vuw.ac.nz)