Biodiversity – Oct. 31/12
- Order Lepidoptera – Moths: Lep means scale and ptera means wing, so these are scale-winged
- Insects in the Order Lepidoptera undergo complete metamorphosis with the stages egg, larva
(caterpillar), pupa, and adult. They have two pairs of membranous wings covered in scales
(synapomorphy). There are 200,000 described species worldwide. Most species are commonly called
moths. Butterflies are a derived group of day-flying moths (is a monophyletic group).
- Lepidopteran phylogeny: Most lepidopterans are moths – all basal groups and some derived groups
are moths. Butterflies are a monophyletic derived group of moths. They are day-flying fancy moths
with clubbed antennae. The most diversity is in the macrolepidoptera.
- Lepidopterans have two pairs of membranous wings covered in scales. They hold their wings in a
variety of positions. All four wings are used in flying. A close-up picture of a lepidopteran wing shows
the scales. The scales are flattened, plate-like hairs. Under the scales is a membranous wing, similar
to a fly wing. The scales come off like dust on one’s finger when a lepidopteran is handled. Colour –
The scales are pigmented, or they have a microstructure that reflects incoming light causing physical
colour, such as iridescence. The Genus Morpho is abundant in Central and South America. It shows
iridescence of its wings (physical colour). Some species have clear patches on their wings, which is a
part of crypsis (camouflage), and they would most likely rest on trees with white bark.
- Most caterpillars are phytophagous/herbivorous, which means they feed on the leaves of plants
(leaf-feeding). A few larvae are serious pests for crops, stored grains, and fabrics. Silk for our silk
fabrics comes from the caterpillar of the silk moth. Adults are beautiful and are symbols of the
environmental movement. They are highly sought after by collectors.
- Lepidopterans have co-evolved with angiosperms (flowering plants): Most caterpillars feed on the
leaves of flowering plants. Most caterpillars are specialized feeders, meaning they feed on only one or
a few species or genera of flowering plants. Adults are pollinators. Adult mouthparts – most have a
long siphoning tube that is coiled at rest, and it is called a proboscis. Proboscis is a modified
mouthpart for specialized feeding, such as drinking the nectar of flowers. The proboscis is coiled at
resting position. Most adults are important pollinators and some are specialized on certain types of
flowers. In the process of eating, they are pollinating. Many caterpillars are exposed-feeders, which
means they feed on leaves while exposed on vegetation. Other caterpillars feed on leaves in a
concealed position, such as in a leaf roll. It is important for them to be camouflaged/concealed.
Caterpillars have a well-developed head, strong chewing mouthparts for munching and crunching
leaves, and silks glands in their mouth. All caterpillars spin silk from their silk glands and they spin
silk on vegetation as they feed.
- Lep/Angiosperm co-evolution: Caterpillars have three pairs of legs on their thoracic segments and
five pairs of prolegs, with crochets, on their abdominal segments. Prolegs are an adaptation to
holding onto vegetation. Crochets are a synapomorphy of larvae (caterpillars). As they walk along the
vegetation, they lay down a silk layer on which they walk. They have crochets (tiny hooks) on their
prolegs, which help them to cling to the silk, and therefore to their host plant. The silk and the
crochets help them to stay on their host plant.
- Lep/Angiosperm co-evolution: Many plants produce toxic secondary metabolites in their leaves.
These toxic substances are meant to deter herbivores. Many caterpillars (and other insects) have
evolved the ability to not only eat these toxic leaves, but to sequester the chemicals in their body and
use them for their own purp