- Phalaena caja Linnaeus, 1758
- Bombyx caja Linnaeus, 1758
- Chelonia caja (Linnaeus, 1758)
Garden Tiger Moth, Great Tiger Moth
No status defined
Value of species
The garden tiger moth is now protected in the UK under the Biodiversity Action Plan (BAP).
The garden tiger moth lives in the northern United States, Canada, and Europe. It prefers cold, temperate climates. The garden tiger moth is found throughout much of the Palearctic, in Europe as far north as Lapland, in Northern Asia and Central Asia, and in North America. In the mountains (Tien Shan), this species is found up to an elevation of 3,000 metres (9,800 ft).
Arctia caja is a northern species found in the US, Canada, and Europe. The moth prefers cold climates with temperate seasonality, as the larvae overwinter, and preferentially chooses host plants that produce pyrrolizidine alkaloids. However, garden tiger moths are generalists, and will pick many different plants to use as larval host plants.
The conspicuous patterns on its wings serve as a warning to predators because the moth's body fluids are poisonous. Their effects are not yet fully known, but these toxins contain quantities of neurotoxic choline esters which act by interfering with the acetylcholine receptor. The colours are also ideal for frightening predators such as small birds - the moth normally hides its hindwings under the cryptic forewings when resting. Between stored toxins, conspicuous warning coloration, and sound cues that are generated mostly as a response to bats, A. caja clearly presents itself as an inedible target for predators.
The garden tiger moth has a wingspan of 45 to 65 millimeters (1.8 to 2.6 in). The design of the wings vary; the front wings are brown with a white pattern (which is sometimes missing), the back wings are orange with a pattern of black dots. There are many aberrations (pattern and colour variants), partly obtained artificially and partly by chance. Oberthür, a French entomologist, mentions about 500 different variants shown in 36 figures. Seitz gives an account of some named aberrations.
This species prefers numerous types of wild habitat, from grasslands to forests. Because of its generalist diet, it is not constrained by features such as host plant location. The only constant quality of a habitat for these animals is that it must be seasonal and cool, and like many members of Genus Arctia, tropical climates do not suit garden tiger moth larvae or adults.
The larvae of A. caja are generalists, meaning they eat a large variety of plants without much specialization. However, most larvae of this species obtain their characteristic toxic compounds from their diet, which can vary from foxglove (and members of the daisy family) to species in completely other plant families, such as plantago.
June. From July to August (or September in warmer climates) the adults are active, primarily at night. Eggs are laid on leaf surfaces and the larvae hatch and feed shortly after the previous generation has died. After feeding for a few months, the larvae go into dormancy while covered in ground matter. In spring, the larvae resume feeding and pupate. By June or July, adults emerge, all from the same generation that was laid in the previous fall. It is key to note that during all life stages there is no generation overlap, either as adults or larvae.
Adults are active from June to September (or August in more northern climates) predominately at night. They have red hairs on their cervical regions with glands nearby and patterning across the wings that is meant to warn and advertise toxicity.