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 This article details the important external morphological features of lepidopterans (butterflies and moths) that are used in their identification.external morphology of  a moth

Asota ficus. Original photo by Omkar Dhavale.

Parts of the Head -

Antennae -

Antennae are the primary olfactory (smell) receptors in insects. The relative size and shape are characteristics used in the identification of lepidopterans.

Compound Eyes -

The colour of the eye as well as the surface texture of the eye (such as being smooth or covered by fine hairs). Apart from a few species of moths most lepidopterans also have two simple eyes

Labial Palpi -

The labial palpi show great variation across the lepidopteran families. They may be separate or connivent (joined along part of their length), they may be erect or porrect (projecting ahead horizontally). The palpi are made up of three segments and presence or absence of minute hairs on the first two segments along with the shape of the apex of the terminal segment (blunt or pointed) are also important.

Proboscis -

The proboscis is a feeding tube made up of two concave half tubes attached together by hooks. These halves can be separated for cleaning by the animal. The shape and relative dimensions of the proboscis are important characteristics used for identification along with other structures that may be present on the proboscis such as spurs on the stem or a pointed apex. The proboscis is only extended when the insect is feeding and is usually coiled under the head.

Body and Limbs -

The body is divided into three large sections, the head, the thorax (to which the limbs are attached) and the abdomen (which contains most of the important internal organs of the insect).

Limbs -

The limbs are made up of multiple sections starting with the coxa that leads to the trochanter, which leads to the femur, the tibia and the tarsus in that order. The relative shape and dimensions of the limbs also represent adaptations different species have obtained to survive in their respective habitats and are thus important with respect to identification.

Wing Morphology -

The relative shape and size of the wings is very important. The different sides of the wing have their own nomenclature.

Sides of the wing -

Costa – This is the leading edge of the wing.

Apex – The anterior corner of the wing.

Termen – The edge of the wing most distant from the body.

Tornus – The posterior corner of the wing.

These terms apply to both forewings and hindwings.

 

external morphology of a moth

 

 

Spirama sp (Owlet Moth). Original photo by Omkar Dhavale.

Structures of the wing -

Wing veins -

The veins of the wing are a system of hollow ducts through which tracheae (respiratory ducts), nerve fibres and blood vessels pass.

Cells -

These are areas enclosed by wing veins.

Ocelli and Lunes -

These are circular and curved in shape respectively. They are usually present near the edges of the wings. Ocelli serve the purpose of mimicking eyes for the purpose of deception of the predators of the animal.  

 

external morphology of a butterfly

 

Lethe europa (Bamboo Treebrown). Photo by Omkar Dhavale. 

 

 

 

 

About the Author of this Article

 

References

Kehimkar I. The Book of Indian Butterflies - Published by the BNHS