Arctiidae is a large and diverse family of moths with around
11,000 species found all over the world, with 6000 Neotropical
species (Scoble 1995). This family includes the groups commonly
known as tiger moths (or tigers), which usually have bright colours,
footmen (which are usually much drabber), lichen moths and wasp
moths. Many species have 'hairy' caterpillars which are popularly
known as woolly bears.
The most distinctive feature of the family is a tymbal organ on the
metathorax (Scoble 1995). This organ has membranes which are
vibrated to produce ultrasonic sounds. They also have thoracic
tympanal organs for hearing, a trait which has a fairly broad
distribution in the Lepidoptera but the location and structure is
distinctive to the family. Other distinctive traits are particular
setae ('hairs') on the larvae, wing venation, and a pair of glands
near the ovipositor (Scoble, 1995). The sounds are used in mating
(Simmons and Conner 1996) and defense against predators (Fullard et
al, 1994).Many of the caterpillars and adults are active during
the daytime. If disturbed, woolly bear caterpillars will roll into a
tight spiral. Common folklore has it that the forthcoming severity
of a winter can be predicted by the amount of black on the Isabella
tiger moth's caterpillar, the most familiar woolly bear in North
America; however the relative width of the black band varies among
instars, not according to weather (Wagner 2005). Isabella tiger
moths (Pyrrharctia isabella) overwinter in the caterpillar stage.
They can survive freezing at moderate subzero temperatures by
producing a cryo-protectant chemical (Layne and Kuharsky 2000). |
