Lepidoptera Totally Explained

The order Lepidoptera is the second most speciose order in the class Insecta and includes the butterflies, moths and skippers. Members of the order are referred to as lepidopterans. A person who collects or studies this order is referred to as a Lepidopterist. This order has more than 180,000 species in 128 families and 47 superfamilies. It is second only to the Coleoptera (the beetles) in number of described species. The name is derived from Ancient Greek (scale) and (wing).

Characteristics of Lepidoptera

Lepidopterans undergo complete metamorphosis going through a four-stage life cycle of egg - larva / caterpillar - pupa/chrysalis -imago/adult. The larvae have a toughened (sclerotized) head capsule, chewing mouthparts, and a soft body, that may have hair-like or other projections, 3 pairs of true legs, and additional prolegs (up to 5 pairs). They can be confused with the larvae of sawflies. Lepidopteran larvae can be differentiated by the presence of crochets on the prolegs which are absent in the Symphyta (sawflies). Most caterpillars are herbivores, but a few are carnivores (some eat ants or other caterpillars) and detritivores.
Adults have two pairs of membranous wings covered, usually completely, by minute scales. In some species, wings are reduced or absent (often in the female but not the male). Antennae are prominent. In moths, males frequently have more feathery antennae than females, for detecting the female pheromones at a distance. Adult mouth parts, called a proboscis, are adapted for sucking nectar. Some species have reduced mouthparts (some species don't feed as adults), and others have them modified to pierce and suck blood or fruit juices (some Noctuids). See also: difference between a butterfly and a moth.

Families of Lepidoptera

There are about 130 families in this order with variations depending on the taxonomic treatment (see the family template box at the bottom of this section).
   The Lepidoptera are divided into several suborders, the largest being Glossata, the vast majority of which are Ditrysia.
   Several other classifications of lepidopteran families are used in older literature. These include the Rhopalocera (club-horned) consisting of what are commonly called butterflies and the Heterocera (varied-horned) consisting of the moths. However, Rhophalocera is a natural (monophyletic) group, while Heterocera is a paraphyletic assemblage.
   Another non-standard classification separates the Lepidoptera into Microlepidoptera for the smaller species (mostly moths) and Macrolepidoptera for the larger species.

Evolution

History of study

Linnaeus in Systema Naturae (1758) recognized three divisions of the Lepidoptera: Papilio, Sphinx, and Phalaena with seven subgroups in Phalaena. He published a study of the Florissant deposits of Colorado. Andreas V. Martynov (1879-1938) recognized the close relationship between Lepidoptera and Trichoptera in his studies on phylogeny. It has long been noted that the Lepidoptera and the Trichoptera (caddisflies) share many similarities that are lacking in other insect orders. Among these are:

females, rather than males, are heterogametic (for example their sex chromosomes differ)
dense setae on the wings (modified into scales in Lepidoptera)
a particular wing venation pattern on the forewings
larvae with mouth structures and glands to make and manipulate silk. Thus the two sister orders are grouped into the Amphiesmenoptera. The group probably evolved in the Jurassic, diverging from the extinct Necrotaulidae. Lepidoptera differ from the Trichoptera in several features, including wing venation, form of the scales on the wings, loss of the cerci, loss of an ocellus, and changes to the legs.

The oldest, most basal lineages of Lepidoptera have as adults, not the curled tongue or proboscis characteristic of most members of the order, but chewing mandibles (Micropterigidae, Agathiphagidae and Heterobathmiidae). Micropterigidae larvae feed on decaying leaves (much like the Trichoptera), fungi, liverworts or live leaves. The adults chew pollen or spores of ferns. In the Agathiphagidae, larvae feed inside seeds of kauri pines, and in Heterobathmiidae the larvae mine leaves of Nothofagus, the southern beech. These families also have mandibles in the pupal stage, which help the pupa emerge from the seed or cocoon just before adult emergence. The Eriocraniidae have a short coiled proboscis in the adult stage, and retain mandibles for the purpose of escaping the cocoon, but they're non-functional thereafter. They, and most of the other non-ditrysian families, are primarily leaf miners in the larval stage. In addition to the proboscis, there's a change in the scales among these basal lineages, with later lineages showing more complex perforated scales.
With the evolution of the Ditrysia in the mid-Cretaceous, there was a major reproductive change. The Ditrysia, which comprise 98% of the Lepidoptera, have two separate openings for reproduction in the females (as well as a third opening for excretion), one for mating, and one for laying eggs. The two are linked internally by a seminal duct. (In more basal lineages there's one cloaca, or later, two openings and an external sperm canal.) Of the early lineages of Ditrysia, Gracillarioidea and Gelechioidea are mostly leaf miners, but more recent lineages feed externally. In the Tineoidea, most species feed on plant and animal detritus and fungi, and build shelters in the larval stage. The Yponomeutoidea is the first group to have significant numbers of species whose larvae feed on herbaceous plants, as opposed to woody plants. They evolved about the time that flowering plants underwent an expansive adaptive radiation in the mid-Cretaceous, and the Gelechioidea that evolved at this time also have great diversity. Whether the processes involved co-evolution or sequential evolution, the diversity of the Lepidoptera and the angiosperms increased together.
In the so-called "macrolepidoptera", which constitutes about 60% of Lepidopteran species, there was a general increase in size, better flying ability (via changes in wing shape and linkage of the forewings and hindwings), reduction in the adult mandibles, and a change in the arrangement of the crochets (hooks) on the larval prolegs, perhaps to improve the grip on the host plant. Many also have tympanal organs, that allow them to hear. These organs evolved eight times, at least, because they occur on different body parts and have structural differences. The main lineages in the macrolepidoptera are the Noctuoidea, Bombycoidea, Lasiocampidae, Mimallonoidea, Geometroidea and Rhopalocera. Bombycoidea plus Lasiocampidae plus Mimallonoidea may be a monophyletic group. The Rhopalocera, comprising the Papilionoidea (Butterflies), Hesperioidea (skippers), and the Hedyloidea (moth-butterflies), are the most recently evolved. There is quite a good fossil record for this group, with the oldest skipper about 56 million years old. Image:Metamorphosis of a Butterfly Merrian 1705.jpg| Painting of butterfly life cycle Image:Butterfly tongue.jpg| Head of Pyralid moth, showing tongue and compound eye Image:Lepidoptera wing.jpg| Close up of wing, showing scales Image:Stathmopoda melanochra (ento-csiro-au).jpg| moth Image:Monarch Butterfly egg.jpg| Egg of Monarch butterfly Danaus plexippus Image:Monarch caterpillar and egg.jpg| Larva of Monarch on milkweed Image:Danaus plexippus chrysalis 2003-10-16.jpg| Chrysalis of Monarch

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