Chalcid Wasps and Monarch Butterfly Caterpillars and Chrysalises

“What happened to my chrysalis?” “Why didn’t my butterfly come out and why is there a tiny hole in the chrysalis?” People often ask about butterfly chrysalises and chalcid wasps.

Chalcid wasp infected Monarch butterfly chrysalises

Chalcid wasp infected
Monarch butterfly chrysalises

Chalcid wasp larvae inside a Monarch butterfly chrysalis

Chalcid wasp larvae
inside a Monarch butterfly
chrysalis

Chalcid wasps in a cup confuse Caden, who knows that butterflies should come from chrysalises, not little bugs he called 'ants'

Chalcid wasps in a cup
confuse Caden, who
knows that butterflies
should come from
chrysalises, not little
bugs he called ‘ants’

Chalcid wasps follow a Monarch caterpillar as it searches for a place to attach itself and pupate

Chalcid wasps follow a
Monarch caterpillar as it
searches for a place to
attach itself and pupate

Chalcid wasps follow a Monarch caterpillar as it searches for a place to attach itself and pupate

Chalcid wasps follow a
Monarch caterpillar as it
searches for a place
to attach itself and pupate

Chalcid wasps lay eggs in a Monarch butterfly chrysalis during experiments

Chalcid wasps lay eggs in
a Monarch butterfly
chrysalis during experiments

When given Monarch chrysalises from a person who was not experienced with chalcid wasps, we knew immediately that there were serious issues with them. They were off-color and softer than normal.

We isolated them from the good chrysalises from the same person.

Instead of Monarch butterflies emerging, chalcid wasps emerged. When one chrysalis was broken open, we could see the chalcid wasp larvae inside.

We have experimented with chalcid wasps, primarily to be able to detect an infected chrysalis that we may find when we buy plants from nurseries that grow their plants outdoors. Many people write to ask us about their empty chrysalis shells that have a tiny hole in them but a butterfly never emerges. We needed photos and detailed personal answers, drawn from our own experiences.

We allowed some of the wasps to emerge in a mesh popup in a sealed room. A video camera was placed in the popup focused on the chrysalis. When the wasps began emerging, the video camera was turned on.

Two of our videos are on YouTube. You can watch the males emerge first by clicking on this sentence. You can watch the females emerge by clicking on this sentence.

Male chalcid wasps are smaller than female chalcid wasps. Male chalcid wasps emerged first. When most male wasps had emerged, a female tried to emerge. Because males are ready to pair as soon as they emerge, they gathered around the opening in the chrysalis, waiting for the females to emerge. When a female approached the opening, males began to bite at the opening to enlarge it. It was too small for a female wasp. As each female emerged, a male would crawl upon her back and begin to touch her antennae, a courtship ritual.

The chalcid wasps that emerged from these chrysalises were moved to another area. Two Monarch caterpillars were placed into the popup with the wasps. One caterpillar was ready to find a place to pupate. The other was two days younger and still wanted to eat. A few milkweed leaves were placed in the bottom of the popup. This was done in a room without other caterpillars.

The older caterpillar immediately headed to the top of the popup and wandered to select a spot to attach itself to pupate. The younger caterpillar crawled to the milkweed leaves and began eating.

Within a few minutes, the wasps were gathering around and on the caterpillar at the top of the popup. Everywhere it crawled, they followed. They totally ignored the younger caterpillar at the bottom of the popup.

The older caterpillar selected its spot, laid its mat of silk, and hung in a J. The wasps stayed on and around it. When it pupated, they began laying eggs in the chrysalis. So many eggs were laid that the chrysalis died within a few days.

It was immediately clear that:

  • over 100 wasps can emerge from one chrysalis
  • they are immediately ready to pair
  • they are small enough to fit through most screen/mesh material that people regularly use in life
  • they smell caterpillars before the caterpillars begin to select a spot to pupate
  • wasps paired immediately and were soon ready to lay eggs in soft chrysalises

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