The Cinnabar Moth (Tyria jacobaeae) is a distinctive day-flying insect recognizable by its striking coloration. This moth is a member of the Erebidae family and is widely distributed across the Palearctic. Its vivid red and black patterns advertise the toxicity shared by both the adult and larval stages.
Current Population and Conservation Status
The Cinnabar Moth is generally considered common and widespread throughout its native European and Western Asian range. It is regularly encountered in open habitats like meadows, coastal dunes, and gardens wherever its host plant is present. Population numbers frequently fluctuate depending on local conditions, which can lead to a perception of local scarcity in certain years.
Despite its widespread distribution, local populations have recently shown significant declines in some areas, such as the United Kingdom. A 2006 report indicated an 83% decline in the UK, resulting in the species being classified as “Vulnerable” within that region. This decline is often attributed to the widespread eradication of its primary food source, Common Ragwort, due to concerns about livestock poisoning.
Identifying Features and Geographic Range
The adult Cinnabar Moth is a medium-sized insect with a wingspan ranging from 32 to 42 millimeters. The forewings are predominantly black, featuring a narrow, bright red stripe along the edge and two distinct red spots near the wing tip. The hindwings are almost entirely red with a thin black border, providing a bold visual warning to potential predators.
The larvae, commonly called caterpillars, are equally conspicuous with their yellow and black striped bodies. These distinct bands signal the caterpillar’s unpalatability. The species is native to Europe and extends across Western and Central Asia to Siberia and China. It has also been intentionally introduced to North America, Australia, and New Zealand, where it is utilized as a biological control agent for invasive ragwort.
The Vital Link to Ragwort
The Cinnabar Moth has a highly specialized ecological relationship with its primary host plant, Common Ragwort (Jacobaea vulgaris). The female moth is stimulated to lay her eggs on the plant, often depositing batches of 30 to 60 eggs on the underside of the leaves. Upon hatching, the larvae feed almost exclusively on the ragwort foliage and flowers.
This diet is crucial because the larvae ingest and sequester the plant’s toxic compounds, specifically pyrrolizidine alkaloids. These toxins are stored within the caterpillar’s body and remain through the pupal stage into the adult moth. The moth’s distribution and density are intrinsically tied to the abundance of ragwort.