Elation ensued when this monarch caterpillar was spotted last week on milkweed in the front yard. Earlier in the month monarch butterflies were spotted visiting the milkweed and depositing their eggs.
Imagine my delight when I discovered the caterpillar had situated itself in the window by the front door to transform itself into a chrysalis and then a butterfly.
Until I came back the next morning to photograph the process and found this...
tachinid fly is a parasitic fly that uses the monarch caterpillar as a host. This bristly, big eyed, slow moving fly stealthily approaches the unsuspecting caterpillar and injects it's fertilized and incubated egg into the caterpillar. The egg then hatches inside the caterpillar and the first instar begins to feed on the monarch slowly killing it from the inside out. Monarch caterpillars are not the only victims, other caterpillars fall prey to this fly as well.
Jenny of Rock Rose solved the mystery. We were chatting Saturday at the monthly Austin bloggers Go-Go and I explained that when the caterpillar began to dry out a silky string was hanging from it's head. She did a little research and forwarded a link to me about the tachinid fly.
What really bums me out is that I didn't dispose of the caterpillar the way I should have and will most likely have more of the pest in my garden. I learned a valuable lesson. When something strange happens, no matter how busy you are, investigate.