Garden tiger moth
The garden tiger moth or great tiger moth is a moth of the family Erebidae. 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.
Description
The garden tiger moth has a wingspan of 45 to 65 millimeters. The design of the wings vary; the front wings are brown with a white pattern, the back wings are orange with a pattern of black dots. There are many aberrations, partly obtained artificially and partly by chance. Oberthür (entomologist)|Oberthür], a French entomologist, mentions about 500 different variants shown in 36 figures. Seitz gives an account of some named aberrations.Garden tiger moth#cite note-3|Geographic range
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, this species is found up to an elevation of.Habitat
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.Food resources
Caterpillars
Host plant preferences
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 to species in completely other plant families, such as plantago.Plant deterrents to herbivory
Because of A. caja’s generalist diet while in the larval stage, it is subject to a wide variety of plant defenses. One study tested plant health with and without beneficial fungus known as Arbuscular mycorrhiza, and saw that Plantago lanceolata with beneficial fungus produce more anti-herbivore toxins, which negatively influenced caterpillar growth. The beneficial fungus gained sugars from the plant, while the plant gained soil nutrients from the fungus, such as phosphorus and nitrogen. Due to the plant-fungus symbiosis, plants were able to produce more toxins than normal due to the fungus’ acquisition of additional usable resources from the soil, and in turn harm the larvae's consumption of leaf matter. The effectiveness of this plant response was tested on several species of Lepidoptera.Adults
Adults primarily consume solely floral nectar, and do not have a noticeable specialty.Life cycle
A. caja hatches at the end of summer, overwinters once, reemerges in spring, and finishes growth by June. From July to August 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. During all life stages there is no generation overlap, either as adults or larvae.Caterpillars
The caterpillars of this species are, like many caterpillars of the tiger moth family, “fuzzy” in appearance, leading them to be called "woolly bears" by casual observers. Once the caterpillars reach a certain size, they acquire hollow tubes that often contain irritating compounds. The larvae depend upon the host plant for their toxic compounds, which they convert from plant defense compounds to larval and adult protection compounds. The caterpillars can grow to a maximum size of 6 cm long.Adults
Adults are active from June to September predominantly 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.Enemies
Predators
While not often eaten due to its toxicity, naïve birds will on rare occasion consume either the adult or larval stages of this species.Parasites
The larval form of A. caja is parasitized by quite a few endoparasites, which usually grow as larvae inside the living host. Examples include:- Carcelia gnava
- Carcelia lucorum
- Carcelia tibialis
- Compsilura concinnata
- Exorista fasciata
- Exorista grandis
- Hubneria affinis
- Pales pavida
- Thelaira leucozona
- Thelaira nigripes
- Thelymorpha marmorata.