Polymorphism in Lepidoptera

Many interesting changes in appearance can be found in the insect order Lepidoptera, which includes butterflies and moths. Polymorphism means that different members of the same species can look different in color and other features.

In Lepidoptera, polymorphism appears in many ways. It can be seen between individuals in the same group, between males and females, and even between groups living in different places or flying in different seasons. Another interesting aspect is mimicry, where some morphs look like other species to stay safe. These changes happen in the overall design of the insects and in traits like wing patterns or body colors.

Genetic polymorphism

Genetic polymorphism happens when different looks in animals are caused only by their genes. One great example is the papilionid great Mormon butterfly, Papilio memnon. This butterfly has four types of males and up to twenty-six types of females. Scientists have studied this butterfly to learn more about how genes cause these differences.

Another example is the scarlet tiger moth, found in Europe, Asia, and southern England. In England, there are three main types of this moth. Scientists have watched these moths for many years to learn how their genes create these different types.

There is also genetic polymorphism in the larvae of Phengaris rebeli. Most of these larvae grow slowly, but a smaller group grows quickly. The slow-growing larvae spend time with ants, while the fast-growing ones finish their growth more quickly.

Sexual dimorphism

Sexual dimorphism is when males and females of the same animal species look different from each other. In butterflies and moths, this difference is very common and is mostly decided by their genes. It can be seen in many groups, especially in the Lycaenidae, Pieridae, and some Nymphalidae. These differences can be small color changes or very different patterns. Some females also have special traits to help them stay safe.

One clear example is in many Psychidae species, where females have very small wings, legs, and mouthparts, while the males have strong wings and special antennae for flying.

Geographical polymorphism

Geographical polymorphism happens when animals living far apart change into different forms.

One example is the Indian white admiral butterfly, which has five different forms. These forms live far from each other, separated by big mountains.

Another example is the Apollo butterfly. Because these butterflies live in small groups and rarely move around, they hardly mix with other groups. This has led to over 600 different forms of the Apollo butterfly, with the size of spots on their wings changing a lot.

Environmental polymorphism

Environmental polymorphism is when animals change how they look because of the weather or season, not because of their genes. In butterflies and moths, this means they can look different depending on the time of year. For example, the common grass yellow butterfly has a darker form in the summer when days are long, and a lighter form after the rainy season when days are shorter. Even caterpillars, like the peppered moth, can change their appearance this way.

Mimicry

Batesian and Müllerian mimicry are common in butterflies and moths. In Batesian mimicry, an edible butterfly looks like an inedible one to stay safe. The viceroy butterfly was thought to mimic the monarch butterfly, but it was later found that the viceroy is actually more toxic than the monarch, making this a case of Müllerian mimicry.

In Müllerian mimicry, toxic butterflies look similar to each other. This helps predators learn to avoid them more quickly. The Heliconius butterflies are a well-known example, as they all look very similar to each other.