Overview of Tiger Moths, Subfamily Arctiinae

Anyone who has used a black light to sample insects at night has probably collected a few tiger moths. The subfamily name Arctiinae is likely derived from the Greek arctos, meaning bear, an apt nickname for the fuzzy tiger moth caterpillars.

Appearance

Tiger moths are often (but not always) brightly colored, with bold markings in geometric shapes. They tend to be small to medium in size and bear filiform antennae. The adults are mostly nocturnal, and hold their wings flat, like a roof over their bodies, when at rest.

Once you've seen a few tiger moths, you will probably recognize other members of the subfamily Artiinae by sight alone. There are, however, some specific wing venation traits used for identification. In most tiger moths, the subcosta (Sc) and radial sector (Rs) are fused to the center of the discal cell in the hind wings.

Tiger moth caterpillars are often quite hairy, which is why some are referred to as woollybears. This subfamily includes some of our most beloved caterpillars, like the banded woollybear, which is believed by some to be a predictor of winter weather. Other members of the group, like the fall webworm, are considered pests.

Habitat

There are about 260 species of tiger moths in North America, a small fraction of the 11,000 species known worldwide. Tiger moths inhabit both temperate and tropical zones but are more diverse in the tropics.

Diet and Life Cycle

As a group, tiger moth caterpillars feed on a wide range of grasses, garden crops, shrubs, and trees. Some species, like the milkweed tussock moth, require specific host plants (in this example, milkweed).

Like all butterflies and moths, tiger moths undergo a complete metamorphosis, with four life cycle stages: egg, larva (caterpillar), pupa, and adult. The cocoon is constructed mostly from larval hairs, making for a rather fuzzy pupal case.

Defenses

Many tiger moths wear bright colors, which may serve to warn predators that they'd be an unpalatable meal. However, the nocturnal tiger moths are also hunted by bats, which find their prey using echolocation rather than sight. Some species of tiger moths have an auditory organ on the abdomen to help them detect and avoid bats at night. Tiger moths don't just listen for bats and flee, though. They produce an ultrasonic clicking sound that confuses and deters the bats pursuing them. Recent evidence suggests the tiger moths are effectively jamming or interfering with bat sonar. Some clever tiger moths that are perfectly tasty will mimic the clicking of their unpalatable cousins, much like the viceroy butterfly mimics the colors of the toxic monarch butterfly.

Classification

The tiger moths were previously classified within the family Arctiidae, and in some cases are listed as a tribe instead of a subfamily. Their current classification is:

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Erebidae
Subfamily: Arctiinae

Sources

• Borror and DeLong's Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson
• Insects: Their Natural History and Diversity, by Stephen A. Marshall
• Moths mimic each others’ sounds to fool hungry Discover Magazine, accessed November 14, 2012
• Moths Use Sonar-Jamming Defense to Fend Off Hunting Bats Scientific American, accessed November 14, 2012
• Moths Mimic Sounds To Survive
• Subfamily Arctiinae - Tiger and Lichen Moths BugGuide.Net, accessed November 14, 2012
• Flying Tigers, Entomology Notes #19, Michigan Entomological Society, accessed November 14, 2012