“I almost wish we were butterflies and liv’d but three summer days – three such days with you I could fill with more delight than fifty common years could ever contain.” – John Keats.
The Lepidoptera are the order of insects that contain the butterflies and moths, and is the 2nd most speciose insect with 180,000 species described (10% of all animal life). Typical lepidopterans possess a long sucking proboscis for mouthparts and minute overlapping scales that cover their entire body and both sides of all 4 wings. The widely recognizable lepidopterans undergo complete metamorphosis, where the larvae pupates and emerges later as an adult moth or butterfly.
IMPORTANCE. The larvae of many lepidoptera can cause severe damage to agricultural crops, and important pest families include tortrix moths, noctuids and pyralid moths. The larvae of Spodoptera (armyworms), Helicoverpa (corn earworms) and Pieris (whites) can all cause extensive damage and to wide variety of crops (polyphagous), including tomatoes and cotton. A few lepidopterans are beneficial, and these include the silkworm moth (Bombyx mori) which have been used to produce silk for generations and various butterflies that people simply just like to look at.
CLASSIFICATION. There is no definitive way to classify lepidoptera or dividing them into 2 groups, as many butterflies are drably coloured and nocturnal and many moths are brightly coloured or day flying. One way of grouping is using the sub-orders zeugloptera, aglossata, heterobathmiina, glossata (non-ditrysians) and glossata (ditrysia), the last of which contains the huge majority of species. Another way of classifying is by size: macrolepidoptera (swallowtail butterflies, emperor moths, etc.) and microlepidoptera (skippers, tortrix moths, etc.), although this grouping is monophyletic.
IDENTIFICATION. The Glossata can be identified by their non-functioning mandibles and elongated maxillary galeae (proboscis). The Ditrysia are identified by how the females have 2 genital openings: one for copulation and another for passage of eggs during oviposition. Further classification into families requires a key. Identification of lepidoptera to species simply by using colour patterns on the wings is not always the best way- some species are mimics of others or can show colour polymorphisms.
POLYMORPHISMS. In several lepidopteran families the sexes can show difference colour and visual attributes (sexual dimorphism), for example in the bagworm moths the females only have vestigial wings, legs and mouthparts whereas the males possess feathery antennae, strong wings and are adept fliers. Differences between individuals of the same species can also occur as geographical polymorphisms, seasonal polymorphisms and polymorphisms due to mimicry of an unpalatable lep.