T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Caterpillar of the Cinnabar moth (Tyria jacobaeae)

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Arctiidae
Genus: Tyria
Species: T. jacobaeae
Binomial name: Tyria jacobaeae
Synonyms: Callimorpha senecionis, Phalaena jacobaeae, Noctua jacobaeae, Hippocrita jacobaeae f. confluens, uchelia jacobaea ab. flavescens
Common name: Cinnabar moth caterpillar

Tyria jacobaeae is a day-flying moth, found in Europe and western and central Asia. T. jacobaeae moths are about 20mm long and have a wingspan of >42 mm. The forewings are a blackish-grey with crimson markings (subcostal and dorsal streaks and two terminal spots), the hind wings are crimson with blackish-grey marking (costal streak, middle of termen, and cilia), while the head, thorax, and abdomen are black.
The moths common named is after the red mineral cinnabar (Mercury sulphide (HgS) because of the red patches on its predominantly black wings. The bright colours of both the larvae and the moths act as warning signs, so they are seldom eaten by predators.

Tyria jacobaeae was introduced into New Zealand in 1929 to control yellow ragwort (Jacobaea vulgaris, Yellow Ragwort), on which its larvae feed during in late spring. It is now found in many parts of New Zealand, including the lower North Island and many areas of the upper South Island. The caterpillar's other food plants are groundsel and cineraria both weeds.

Yellow ragwort is full of alkaloids when are produced by the plant as a defence mechanism against insect herbivores. Some people can have a reaction by just touching the leaves. This plant is toxic to cattle and horses due to the pyrrolizidine alkaloids (PAs) which damage the livers leading to irreversible cirrhosis. Tyria jacobaeae caterpillars are not affected by them and they absorb them and they themselves become toxic. Very few birds will eat them.

A female moth lays up to 300 yellow spherical eggs, usually in clusters of 30 to 60 on the underside of ragwort leaves. Initially, the larvae are pale yellow, but later larval stages develop the jet black and orange/yellow striped colouring. They can grow up to 30mm, and are voracious eaters; large populations can strip entire patches of ragwort clean. After about a month the caterpillars pupate. 

The caterpillar's effect on ragwort numbers is not great because there is only one generation a year and the caterpillars feed only for a few weeks. The ragwort keeps flowering much longer than that so seeds are still produced. 
The caterpillars of this species practice cannibalism when they run out of food.

The caterpillars of the Cinnabar moth devouring the flower heads of the yellow ragwort (Jacobaea vulgaris) 

Tyria jacobaeae's caterpillar.

The moth of Tyria jacobaeae

Thanks to Wikipedia for text and Information: