What is a butterfly or a moth?

Both moths and butterflies belong to the Order Lepidoptera and are characterised by the presence of a covering of scales (modified hairs) that covers the two pairs of wings like the tiles on a roof. The colourful appearance of different species of this Order has partly helped to captivate collectors for a long time, making it the best-known group of insects. The number of species existing throughout the world is still unknown and new species are discovered for science every year (even in Europe). Duckworth (1975) refers to an approximate number of 165 thousand described species, 10% of which are diurnal. Young (1997) refers to 130 thousand known species, 12% of which are diurnal butterflies.

 

More than 4300 species are described in the Iberian Peninsula and, despite Portugal being 3 to 4 times smaller than neighbouring Spain, it has already over 2700 species, which makes up more than 55% of the Iberian Lepidopterofauna. Around 95% of the species described for Portugal belong to the group of moths/micromoths and the remaining 5% belong to the group of butterflies.

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So what is the difference between a butterfly and a moth?

The first idea that comes to us is that it must be biological activity that differentiates them, however, although butterflies fly exclusively during the day, the same is no longer the case with moths as most of them fly both at night and day. In evolutionary terms, we also get the idea that diurnal species will be the most evolved, but this is also not true, as they are sandwiched in the middle of the evolutionary tree. However, something exists that, despite being quite relative, makes them different. The main structural characteristic that distinguishes diurnal from moths is the shape of the antennae. In the butterflies they are almost always club-shaped and in the moths they are filiform or pectinate. Another characteristic is the absence of the frenulum (thread that joins the front and back wings) on butterflies.

 

More controversial is the division of the Order into microlepidoptera and macrolepidoptera. Despite having an invalid scientific nature, this distinction continues to be used as it is quite practical. Following the classification grid, all species of butterflies and the following moths, normally larger in size, are considered macrolepidoptera. Microlepidoptera will then be all the species that remain on the classification grid up to daytime butterflies.

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However, some families included in the microlepidoptera are considered to be similar to macromoths (Hepialidae, Zygaenidae and Sesiidae). It is important to note that despite the use of this division by all aficionados, there are species of microlepidoptera that are larger than some moths.

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Butterfly life cycle

We all learned in school that butterflies are a classic example of complete metamorphosis. Egg-caterpillar-chrysalis-adult. However, in the world of moths there are some exceptions. Females of several species of the genus Coleophora (micromoth) deposit fully formed caterpillars directly on their target plant. It is known that butterfly reproduction is mostly sexual. Here in the world of night butterflies there are exceptions too. Some members of the Nepticulidae family have the ability to perform parthenogenesis (asexual reproduction). This is a specific characteristic of the Psychidae family. In this family, only males have wings, females, in addition to not having wings, may also have missing legs, antennae and even eyes.

 

Identification

For the beginner, nothing is more frustrating than not being able to identify a species, whether it be a butterfly, a plant or a bird. For a specialist nothing is more exciting, as it could be something new or quite rare. The first step is to start with groups. The study of moths should begin with macrolepidoptera. This group includes butterflies that, in general, display patterns and colours that allow identification without the need for capture and laboratory analysis. A simple photograph may be enough so that, using the help of a more experienced lepidopterologist, the specimen can be identified. In addition to the vast bibliography that exists throughout Europe, you can now use online field guides to moths. The same is no longer true of micromoths. This group includes small and very similar species within the same genus, which can only be identified by microscopic observation of the genital tract. Many species of micromoths are easily identified at earlier stages of their life cycle. Some caterpillars live inside the leaves of their target plants and thus draw lines, called mines, with specific characteristics for each species. However, despite the difficulties in identification, the study of micromoths is perhaps one of the most interesting. Given that most of the new species discovered in recent years are micromoths, any lepidopterologist would like to see their name on a species new to science. Unfortunately, the existing bibliography is limited and is also somewhat expensive.

 

The simplest way to identify a butterfly is to flip through the pages of a field guide with photos of different species. Any beginner will find it quite confusing, given the large number of species that seem very similar to each other. Many field guides present the butterflies prepared and therefore in an unnatural position, which makes identification even more difficult. In addition to the wings, other parts of the body such as the antennae, legs and abdomen can be essential in the search for species identification. Typical wing patterns are also altered in prepared specimens. However, visualisation of the hind wings is also important in identifying some species. There are other important points in using field guides. Normally all species are represented with specimens in excellent condition, that is, with the wings in perfect condition, as if they had just been born. However, not all individuals observed in the field are in this perfect condition, the wings may be damaged, the colours more faded, the spots or lines less marked or there being a complete absence of scales. Sometimes it becomes impossible to identify the specimen based on external characteristics, but examination of the genitalia is always successful.

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Variable species

Some butterflies have two or more distinct shapes (polymorphism), that is, maintaining the shapes of the marks and lines on their wings, they may be darker, lighter or even different colors. Ex: Omphaloscelis lunosa. Therefore, it is necessary to look at the specimen carefully, looking more at the details of the size, shape and pattern of the wings than at the color itself. Variation in color or tone may highlight lines, dots or eyespots, however the pattern and arrangement of these characteristics remain in the same place. If we are faced with an individual with characteristics of two or more species, the ideal is to make a list of the likely species and look for different images in various field guides.

If distinction is impossible, the characteristics of each species can be used, such as: flight period, distribution, habitat, target plant presence, etc. In any case, and if you don't want to capture the specimen, you can always resort to photography. You should photograph from different angles trying to highlight the most prominent features.