Butterfly Anatomy : Part 3

Butterfly Anatomy : Part 3
Interior Regions of Butterfly Wings

In Part 1 and Part 2 of the previous weeks' articles on butterfly anatomy, we learned about the naming of the various parts of a butterfly. In particular, the names of the external margins of the wings and the wing venation naming convention based on the Numerical Notation system. By now, we should be familiar with the terms like termen, costa, tornus and so on, which are descriptors of the external margins and angles of the wings.

In this article, we move into the interior regions of the wings and learn about the terminology that are associated with the different parts of the wings. As a recap to why these terms are important, even to amateur hobbyists, the following reasons come to mind :

• An understanding of the naming convention means that the positions of the spots, bands, lines, and various features can be accurately described.
• The descriptions of diagnostic features on a butterfly's wings in publications and scientific write-ups can be properly understood and the reader will know where to look and compare these markings if he/she understands the anatomical terminology.
• Learning the names of various parts of the wings can also help an observer describe a feature properly so that these can be related to others to help ID a butterfly species. The proper names of these parts is likened to a "GPS" to locate different features on the wings e.g. "there are three sub-apical spots on the forewing", would immediately focus on the forewing, and spots that are just adjacent to the apex of the wing.

The basic internal regions of a butterfly's forewing and their associated anatomical names

Let us now take a look at the forewing of a butterfly, and familiarise ourselves with the names of the various parts of the interior regions of the wings. I will separate the forewing into 3 main regions so that each part is treated in installments to better focus on the areas under discussion. Then an actual butterfly photo is used as an example to illustrate the area concerned. However, it is important to note that these areas are not scientifically precise and is only a rough estimate of the part of the wing.

At this juncture, it is important to take note of the prefixes "sub-" and "post-". When the prefix "sub-" is used, it means the area that is closer or towards the body of the butterfly, and if "post-" is used, the area is further away from the body of the butterfly.

In many butterfly species, the apical area often contains important features that are diagnostic. This is the area that is near the apex of the forewing. Adjacent to the apical area is the sub-apical area where many features are also found which aid in the identification of butterflies.

Some examples illustrating apical and sub-apical features on the forewing of a butterfly

An example of a species with a diagnostic apical area is the Knight (Lebadea martha parkeri) which features "prominent white apical area" that distinguishes it from the female, which does not have its apical area whitened. In the 2nd example, the Common Three Ring has "a large yellow-ringed sub-apical ocellus".

The next region of interest would be the internal margins or "edge" areas of the wings. These are the costal area (at the costa of the forewing), the dorsal area (at the dorsum of the forewing) and the basal area (at the base of the forewing). The area next to the basal area is the post-basal area (further away from the body, hence "post-"). The outer wing edge is called the marginal area and the area next to it is referred to as the sub-marginal area.

Examples illustrating the various terms like marginal, sub-marginal, costal, basal and dorsal parts of the forewing of a butterfly

The examples shown of actual photos of various species showing the diagnostic costal spot of the Forget-Me-Not (Catochrysops strabo strabo), the creamy patch on the dorsal area on the forewing of the female Malay Lacewing (Cethosia hypsea hypsina) and the basal area of the Gram Blue (Euchrysops cnejus cnejus) a pale shining blue.  Note the features on the marginal and sub-marginal areas of the Malayan Lascar (Lasippa tiga siaka)

On the interior region of the forewing, are the areas that are associated with the wing cell. The cell (or disc) has been described in Part 2 with the wing venation. The areas around the cell is usually called the discal area. The area that is further away from the butterfly's body is referred to as the post-discal area, whilst the part that is nearer to the body is called the sub-discal area.

Features in the discal and post-discal parts of the butterfly's forewing

In the examples shown, the orange discal patch on the forewing above separates the male of the Dark Posy (Drupadia theda thesmia) from the females and other species of the genus. The Banded Yeoman features a broad orange-yellow post-discal band on the forewing.

The basic internal regions of a butterfly's hindwing and their associated anatomical names

Now let us take a closer look at the hindwing and the terminology of the various parts of the wing. As the wing surface of the hindwings of most butterflies is smaller than the forewing, there is no post-basal area on the hindwing.



Of particular interest is the tornal area of the hindwing. This area carries many diagnostic features like ocelli, tails and a series of markings that help in the identification of Lycaenidae butterflies. The tornal area is near the tornus of the hindwing.

The tornal area of Lycaenids usually have key distinguishing features that are used in the identification of butterflies

An example of the diagnostic feature of the orange-crowned ocellus and long tail at the tornal area of the Silver Forget-Me-Not (Catochrysops panormus exiguus), compared to the twin orange-crowned ocelli and short tail of the Gram Blue (Euchrysops cnejus cnejus).

Next, we look at the margins of the hindwing that are somewhat similar to the forewing, with the marginal, sub-marginal, costal, dorsal, and basal areas.

A few quick examples here are the Tawny Coster (Acraea terpsicore) with the white spots on a black marginal border, and the Dwarf Crow (Euploea tulliolus ledereri) with a row of white marginal and sub-marginal spots. In the Pointed Ciliate Blue (Anthene lycaenina miya), the large costal spot on the hindwing is a diagnostic feature to separate it from the similar-looking Ciliate Blue.

Finally, the interior region of the hindwing features the discal, sub-discal and post-discal areas of the wing that are associated with the section that encompasses the cell of the hindwing. Like in the forewing, this area often has many spots, stripes, bands and other features that help to identify a butterfly.

Focus on the discal features on the hindwing of these Neptis spp to better understand the differences between them

In the example shown here, the white discal band on the hindwing of the various Neptis spp. is diagnostic and helps to distinguish the various species found in Singapore. The post-discal band on the fore- and hindwing of the Bush Brown (Mycalesis spp) is an important feature that helps to separate the many lookalike species in the genus.



With the knowledge of these basic terminology used in a butterfly's anatomical features, a hobbyist can now combine the key descriptors in terms of wing margin names, venation (and spaces between veins) and interior regions of the wings to better understand how the physical features of a butterfly are described and where to look for specific diagnostic markings to help in the identification of different species of butterflies.  These 3 blog articles are by no means exhaustive and an enthusiast who is interested should continue to equip him/herself with a glossary of terms beyond these basic anatomical terminology of butterflies.

Text by Khew SK : Photos by Antonio Giudici, Khew SK, Bobby Mun and Jonathan Soong.  

Line diagrams of butterfly wings from Butterflies of West Malaysia and Singapore by WA Fleming.

Previous articles in this series :

• Butterfly Anatomy : Part 2 - Wing Venation on a Butterfly's Wings
• Butterfly Anatomy : Part 1 - Scientific Names For Different Parts of a Butterfly

Butterfly Anatomy : Part 2

Butterfly Anatomy : Part 2
Wing Venation on a Butterfly's Wings

The prominently darkened veins on the hindwing of the Common Birdwing illustrates the wing venation and all the veins that originate from the cell

In the next article of our series on butterfly anatomy and scientific terminology, we take a closer look at the wings of the butterfly. The wings constitute one of the important parts of a butterfly in classification and identification work. The ability to understand the terms that are used to reference various parts of a butterfly's wings is critical to butterfly identification. This article focuses on the veins on the butterfly's wings and how they are named.

This backlit shot of a Lemon Emigrant shows the vein structure and arrangement clearly

The wings of a butterfly are membranous with veins running longitudinally from the base (where the wings are attached to the thorax) to the outer margins of the wings. The pattern and arrangement of these veins (wing venation) is an important diagnostic tool in the identification of butterflies. It is therefore important to understand the wing venation as a reference to locating features that are associated with the veins/spaces on a butterfly's wings. In some cases, the arrangements of the veins themselves will give important clues to the genus of the butterflies.

The raised veins are prominent in this Malay Lacewing and show clearly how the veins are arranged

The veins of a butterfly's wings gives the structural strength to the soft membranous wings onto which the scales are attached. These veins are tubular, in which a liquid 'blood', or haemolymph circulates within them.

The Comstock system of butterfly wing vein notation.  Whilst the system has a strong scientific basis, the numbering system requires a bit of understanding and is not easy for a hobbyist enthusiast to understand.  It is probably for this reason that, for butterflies, it is easier to understand the more intuitive Numerical Notation system.

A butterfly's wing venation has been used extensively in the classification and identification of butterflies and the nomenclature of the veins in insects usually follows the system adopted by JH Comstock (referred to as the Comstock, 1918 system). However, a simplified and more intuitive Numerical Notation system pioneered by Herrich-Schaffer is more commonly used. Basically, this system numbers the veins from 1, which represents the anal veins (1a and 1b) through to number 12 on the forewing, and 1a and 1b to 8 on the hindwing. Note however, that not all butterflies have the full set of veins on both wings, and may vary from species to species.

A typical wing venation of a butterfly based on the Numerical Notation system. Note the naming of the spaces between the veins 

In the Numerical Notation system, veins 2 to 11 on the forewing and 2 to 7 on the hindwing originate from the cell. The remaining veins originate from the wing bases. The interspace between two veins is known by the number of the lower vein. E.g. the space between veins 2 and 3 is referred to as "space 2".


In the identification of a Dingy Line Blue, the reference to the ocellus in space 2 being a diagnostic feature is clearer when one is able to find "space 2" on the hindwing by understanding the numerical naming of the wing venation and spaces between the veins.

This is an important convention to understand, as for example, the description of "the ocellus in space 2 of the hindwing is moved inwards" immediately directs the observer to that particular part of the wing to observe this diagnostic feature that distinguishes the Dingy Bush Brown (Mycalesis perseus cepheus) from its other lookalike cousins.

In the examples below, we illustrate how wing venation is used to refer to certain features of a butterfly. We will compare a few photographs of actual butterflies with the numerical system of naming the veins and how these wing veins appear in the actual individuals.

The Common Rose (Pachliopta aristolochiae asteris) - Species of the family Papilionidae tend to have the full complement of veins from 1a to 12 on the forewing and 1a to 8 on the hindwing (with vein 1b missing).


Diagrammatic representation of the wing venation of the Common Rose

For example, when a description of the Common Rose states "there is a spatulate (spoon-shaped) tail at vein 4 of the hindwing", it is now easy to look at the veins and understand where the location of the tail at vein 4 is.

The Striped Blue Crow (Euploea mulciber mulciber) - The Danainae feature species that have almost the complete complement of wing veins on both wings, with the exception of vein 1a on the forewing. In the case of this male Striped Blue Crow, the veins are clearly seen on the brownish base colour of the wings.


Diagrammatic representation of the wing venation of the Striped Blue Crow

Take a close look at the hindwing veins on the butterfly. Can you trace all the veins from vein 2 to vein 7 to the cell on the wing? On the hindwing in all butterflies, veins 2 to 7 always originate from the cell.

The darkened veins of the Painted Jezebel are helpful in locating and understanding the position of the veins on the wings.

The Painted Jezebel (Delias hyparete metarete) - Many species of the Pieridae feature the full complement of veins from 1a to 8 on the hindwing. However, several veins are missing from the forewing, where veins 1a, 8 and 10 are not present.


Diagrammatic representation of the wing venation of the Painted Jezebel

The Painted Jezebel, like several species in the Pieridae family, is also interesting in that the veins on the wings are darkened and it is quite easy to trace most of the veins in the butterfly when looking at its wings.

The Common Posy (Drupadia ravindra moorei) - A example of a Lycaenidae and the wing veins in this species. Many species in the Lycaenidae family have veins 8 and 9 are missing from the forewing.


Diagrammatic representation of the wing venation of the Common Posy

Looking at the hindwing veins, a description such as "the hindwing has three white tails at veins 1b, 2 and 3, of which the longest is the one at vein 2" becomes easier to understand.

In the next article, we will discuss the names of the different parts and zones on the wings of a butterfly and how we can use these references together with the wing venation and external margin names of the wings to find the diagnostic features in the identification of butterflies.

Text by Khew SK : Photos by Sunny Chir and Khew SK : Wing venation diagrams taken from Butterflies of the Malay Peninsula by Corbet and Pendlebury, 4th edition

Butterfly Anatomy

Butterfly Anatomy : Part 1
Scientific Names For Different Parts of a Butterfly


Names for the different parts of the forewing of a butterfly

In the appreciation of butterflies, nature's winged jewels, it is also important to be able to appropriately refer to the correct names to the different physical parts of the butterfly. Just like any bird, animal or even an inanimate object, like a car, there are proper names given to each part so that anyone describing or referring to the different aspects or parts of it can be universally understood.

Names for the different parts of the hindwing of a butterfly

This is no different for a butterfly, which has proper terms to describe different parts of its wings or body. In this blog article, we will systematically learn about the different parts of a butterfly from basic terminology to the detailed biological terms used by scientists to describe a butterfly's physical attributes. This article is not meant to be comprehensive or exhaustive, as a complete glossary of the scientific terminology may be too daunting for a hobbyist trying to learn about the proper names given to the different parts of a butterfly.

In many references, both online and in hardcopy books, diagrams and graphics depicting the different parts of a butterfly are often too complicated. This may be due to packing in as much information as possible for efficiency, where a lot of information is crammed into a single picture. I will attempt to introduce the anatomical features of a butterfly and their respective proper names progressively from the commonly used terms to more detailed scientific terminology.

Firstly, when one takes a look at a butterfly, the basic information would be the body and wings of the insect. Fundamentally, the body is divided into three segments - the head, thorax and abdomen. Then we take a look at the wings. All butterflies have four wings - left forewing, right forewing, left hindwing and right hindwing.

At the next level, would be the different parts found on the head, thorax and abdomen. These are important parts of the butterfly and often described or elaborated in references as part of the diagnostic features in butterfly identification. For example, the colour of the shaft of the antenna just after the club is a diagnostic feature for some skippers, whilst the shape of the tip of the abdomen can help to separate between a male and female of a species of butterfly.

Hence on the head, the important parts that should be highlighted are the antennae, eyes, palpi and proboscis. The middle section of the body, the thorax, is best thought of as a muscular anchor to which the head, legs, segmented abdomen, and wings are attached. The abdomen contains the digestive system, breathing apparatus, a long tubular heart, and the sexual organs. The abdominal exoskeleton is multi-segmented. Each of the 10 segments is comprised of a ring of a hard material called chitin. The segments are linked by flexible tissues, allowing the abdomen to bend, a necessity for copulation and egg-laying.

Upperside and underside of the wings of the same butterfly

Moving to the next level of detail, would be the wings and the correct names for different parts of the wings. Firstly, when we refer to the upperside (or dorsal) and underside (or ventral) side of the wings, the photos above indicate the convention for this. And then, considering that a butterfly's wing is triangular-shaped, each margin and angle has a given name.


Names for the external margins of the forewing and hindwing of a butterfly

Hence a butterfly enthusiast should familiarise himself with the names of these parts of a butterfly's wings. This is because when taxonomists describe the features of a butterfly's wings e.g. "the forewing apex is rounded in the female...", one will know exactly where to look at, and which part of the wing the description is referring to.



The terms apex, termen, base, tornus, dorsum and costa should be the next taxonomic terms that an enthusiast should know and remember. These are the general terms applied to the external edges of a butterfly's wings and are quite key to describing the wings.



When the description refers to the forewing dorsum margin (straight or curved) of the Dwarf Crow, an observer will be able to focus straightaway on the correct part to see the differences described.

In subsequent parts of this Butterfly Anatomy series, we will go into the wing surfaces, veins and internal taxonomic names for different parts of a butterfly's wings, and other detailed names of other different parts of a butterfly that is often used as descriptors and diagnostic features to identify different species. A glossary of other commonly used taxonomic terms will also be discussed.

Text by Khew SK ; Photos by Bob Cheong, Khew SK and Loh MY

Lancers of Singapore

Lancers of Singapore
Featuring the Lancer skippers


The rare Yellow Chequered Lancer (Plastingia pellonia) perches on a leaf

This weekend's blogpost focuses on a group of butterflies in the Hesperiidae family (Skippers) that are collectively given the common English name of "Lancer". As shared in earlier posts on this blog regarding the interesting backgrounds in which the early collectors coined common names for butterflies, we have to sometimes do a bit of "forensic" analysis of some of these names to try to understand how some of these names originated.

The Yellow Vein Lancer (Pyroneura latoia latoia) is often observed at the flowers of the Bandicoot Berry (Leea indica) in the forested nature reserves of Singapore

Doing an online search for the meaning of "Lancer" would turn up primary definitions like "A soldier of a cavalry regiment armed with lances" or "a soldier who belongs to the part of an army that used lances in the past." The keyword in this case focuses on the word "lance" which is usually a long-handled weapon that is in the form of a spear. So the obvious etymology of the word "lancer" centres on a military personnel brandishing a long weapon.


A Chequered Lancer (Plastingia naga) perches in the shaded understory of its favourite habitat

So why would a butterfly have anything to do with a "Lancer"? This is the part that is probably more difficult to establish, and we can only speculate without any guarantees of a definitive conclusion, as there are often multiple viewpoints from which an observer can come to his own inference regarding a name.



Skippers, the collective name given to butterflies of the Hesperiidae family, are usually stout-bodied, moth-like in appearance and fast flyers. The individual species that are referred to as "Lancers" vary across different genera. But like most species of the family, they are skittish and zip around with great speed. Perhaps the early collectors saw in these species, a military-like demeanour in their wing shape and flight reminding them of soldiers brandishing lethal-looking weapons? A bit challenging to try to imagine these beautiful gentle creatures in that light, but to each his own.

The Chequered Lancer (Plastingia naga)



The first species that we feature here is the Chequered Lancer (Plastingia naga). That the Chequered Lancer is referred to by only its species name suggests that the butterfly is consistent throughout its geographical range with almost no perceptible differences in its appearance across the different countries where it occurs.



The underside of the Chequered Lancer has an attractive pattern of black veins and white rectangular spots. The upperside is a medium brown with hyaline spots on the forewings and yellowish streaks on both wings. The abdomen is striped black-and-white whilst the antennaa has a whitish band just after the club.


A Chequered Lancer sunbathes in the late afternoon showing its uppersides

A Chequered Lancer perches on the upperside of a leaf of its caterpillar host plant, Fishtail Palm (Caryota mitis)

The Chequered Lancer prefers well-shaded forest habitats where it perches on the top surfaces of leaves. It flies off rapidly when disturbed but often not too far away from its preferred habitats. The caterpillar of this species has been successfully bred on the Fishtail Palm (Caryota mitis) in Singapore.

The Yellow Chequered Lancer (Plastingia pellonia)



The Yellow Chequered Lancer is closely related to the Chequered Lancer and belongs to the same genus. It can be found in the same heavily-shaded habitats as the Chequered Lancer, but is much rarer, and usually spotted deep in forested areas within the nature reserves of Singapore.


A Yellow Chequered Lancer extends its palpi making it appear strange

The Yellow Chequered Lancer has a similar pattern on the underside of its wings to the Chequered Lancer, but instead of white spots, the overall ground colour of the butterfly is black-and-yellow, instead of black-and-white. The wings above are quite similar to the Chequered Lancer, but the spots are generally larger and more prominent.



The butterfly is considered very rare and its life history has hitherto not been recorded yet. The caterpillar host plant is very likely one of the jungle palms or even rattan, and it is hoped that we can document its full life history one day in the near future.

The Yellow Vein Lancer (Pyroneura latoia latoia)



At a glance, the Yellow Vein Lancer can look quite similar to the Yellow Chequered Lancer. However, upon a closer look, the differences are obvious and the two species can be separated quite easily. The butterfly is another forest-dependent species that is usually found within Singapore's nature reserves. Where found, sometimes several individuals can be spotted in the same locality, especially when the butterflies are feeding on the flowers of the Bandicoot Berry (Leea indica).


A glimpse of the upperside of a Yellow Chequered Lancer as it sunbathes in the warm sunshine


The Yellow Vein Lancer is dark brown on the upperside and the forewing has a series of pale yellow hyaline spots and streaks. The hindwing has a series of hyaline discal spots overlaid by a yellow band. On the underside, the veins are prominently marked in yellow with large spots and streaks between the veins. The antennae are yellowish from the apiculus to just behind the club, and the abdomen is striped black-and-yellow.



The species is moderately common in the nature reserves, and the caterpillars have been successfully bred on the Nibong Palm (Oncosperma horridum) that can be found in forested areas within the Central Catchment Nature Reserves.

The Pugnacious Lancer (Pemara pugnans)



The Pugnacious Lancer is the sole representative of the genus in the Southeast Asian Region. It is very rare in Singapore, and found mainly in forested areas within the nature reserves. Where observed, it is usually perched on the upperside of leaves with its wings folded upright. It is skittish like most skippers and tends to "jump" when it is photographed with a flash.


The upperside of the Pugnacious Lancer, showing the unique arrangement of the forewing spots


The species is dark brown above with a series of pale yellowish hyaline spots on the forewing. The underside is orange-brown and generously overlaid with ochreous scaling on both wings. On the forewing, there is a pair of black sub-apical spots adjacent to a single yellowish hyaline spot. The antennae are blackish brown throughout.


A Pugnacious Lancer perched on the upperside of a leaf with its wings folded upright

The caterpillar host plant of the Pugnacious Lancer is still unknown and given its rarity, it is hoped that a chance encounter of an ovipositing female of the species can fill in the gap in our knowledge of the early stages of this butterfly.

Text by Khew SK : Photos by James Chia, Goh LC, Khew SK, Koh CH, Nelson Ong and Jonathan Soong