InsectNet forum

What used to be a common sight years ago, I haven't run across these guys in years, Tyria jacobaeae, introduced to control tansy ragwort,Senecio
jacobaea, a plant toxic to livestock, they did a good job of it, now these are a rare sight.

I didn't know you had those in the States! Here in southern England they were a common sight when I was a kid, almost every ragwort plant had them. Now I hardly ever see them, and none in the last two or three years.

Their population numbers are very dynamic. Many years you don't see them much and some years they are everywhere. Since 2009 I can remember 2 years when they were common. I also didn't know that they exist in NA.

The first time I found this caterpillar in Brittany (NW France), where it is very common on the coast, I was 7 years old and thought I found some Danaus plexippus in France ! I was very proud of myself as plexippus caterpillars have never been found in France AFAIK.