Years ago I used to work on various aspects of biological control of weeds in New Zealand. One of the the target weeds was ragwort, and although the programme has had reasonable success in some areas, mostly because of the introduction of the ragwort flea beetle, ragwort is still common (too common) in some parts of New Zealand. This caterpillar, the larva of the cinnabar moth, was introduced into New Zealand in the early 20th century but had little effect on the ragwort problem. After redistribution efforts in the 1980s, it's now much more widespread and probably contributes to ragwort control in some areas.
This, however, was the only caterpillar I saw near the top of the No. 1 Line road a few days ago, so the flourishing ragwort population will no doubt remain untroubled by cinnabar moth depradation, at least for this season.
All content © 2014 Pete McGregor