Indigenous Nursery News Blog

Butterfly Gardening Notes 1 - Parasitised Caterpillars

Have you ever seen those strange looking caterpillars with tiny white "spikes" on its back? We are often asked if caterpillars carry eggs on their back, and so we decided to ask a butterfly expert for more information.

Steve Woodhall, master Lepidopterist, regularly helps us at Random Harvest Indigenous Nursery to answer questions on anything butterfly or caterpillar related. Here is what he said about this strange creature. The white egg-like things on the hairy caterpillar (which is probably a Tricolored Tiger Moth, Rhodogastria amasis) are Braconid wasp cocoons.

Caterpillars Butterfly gardening

Braconid Wasp Cocoons

These are parasitoid wasps whose adults inject eggs into the bodies of their prey, which is usually but not always a lepidopteran (butterfly) caterpillar.

Some inject multiple eggs; others’ eggs begin dividing into cells as normal fertilised eggs do, but at some point, those cells split up into a group of clones, which then go on to develop into independent embryos.

With the eggs, the female wasp usually injects a special virus from her own genome, called a polydnavirus, which suppresses the caterpillar’s immune system and prevents its antibodies from killing the parasitoid larvae when they emerge inside the host. Science fiction has often made use of these lifestyles to imagine some really nasty lifeforms (such as the Alien)!

The brownish larva on the grass seedhead has probably fallen victim to another predator – a microbe of some sort.

Butterfly-gardening Natural-pest-control

The best known are:

  • Nuclear Polyhedrosis Virus
  • Pseudomonas bacteria
  • Bacillus thuringiensis (some people deliberately spray caterpillars with this – Kirchhoffs sells a version under their ‘Margaret Roberts’ brand, which I am sure has that lady spinning in her grave). These make the caterpillar turn black or brown, and die by dehydration as it dissolves from the inside.

It might also be a fungal parasite, which may turn the caterpillar into a zombie that crawls up to a prominent perch before dying when the fungus fruiting body emerges. The fungus spores may then infect a secondary host.

Gardening to attract butterflies

Gardening to attract butterflies will, by default, bring the caterpillars. It is vital to make the connection between inviting butterflies into your garden and providing something for their larvae (caterpillars) to eat.

At Random Harvest Nursery you are able to choose from a vast selection of South African Indigenous Plants that will attract butterflies to your garden. It is not enough to garden with Nectar providing plants for butterflies. It is essential that you provide host plants for butterfly larvae as well. You can either ask one of our friendly, knowledgeable staff for assistance in selecting butterfly attracting plants, or you can book an appointment for our staff to assist you.


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