25 November 2018

Butterfly Anatomy - Part 4

Butterfly Anatomy - Part 4
Glossary of some Anatomical Terms

In this final weekend article for the month of November 2018, we discuss some common anatomical terms that we often come across in the description of butterflies. This short list is accompanied by photos of butterflies and highlights the areas that are described by these anatomical names for different parts of the butterflies that were not dealt with in the earlier articles in this series. 

Doing an online search for glossaries of anatomical names of butterflies should yield many comprehensive lists that a serious student would find more complete. This article features 10 commonly used terms that are found in books, scientific papers and online articles used to aid in the description of the physical morphology of butterflies and in many cases, to highlight distinguishing features to separate the IDs of different species.

1. Apiculus

The is the tapering apical portion of the antennal club of Hesperiidae species (Skippers). The apiculus or "hook" at the end of the antenna is unique to the Hesperiidae family and is not present in the other butterfly families found in Singapore. However, it should be noted that in some genera of the Hesperiidae, like the Taractrocera spp. this apiculus is missing.

It should be noted that the apiculus is not exclusive to butterflies' anatomy, and from definitions on online dictionaries, the word is applied to the pointed ends of a range of other organisms and plants, e.g. part of a spore or a small point formed by the projection of the midrib beyond its leaf.

2. Brand

The brand in butterfly anatomical terminology usually refers to a secondary sexual characteristic, usually found in male butterflies. The brand in butterflies is a patch of specialised androconial scales of the male forewing that helps disperse pheromones (used to attract females) emitted from tiny organs on the wings.

Examples of these sex brands are the distinguishing features on the hindwing of the Common Tiger (Danaus genutia genutia), the circular disc that can be seen on the underside of the Common Red Flash (Rapala iarbus iarbus) and a line in the forewing of the Small Branded Swift (Pelopidas mathias mathias).

3. Cilia

In butterflies, the cilia refers to the short fine hairs which form the fringe along the wing termens (or margins). For some species of butterflies, the colour of the cilia are diagnostic features that help to ascertain the ID of the species. In others, for example in the Anthene spp, extensions of the hindwing cilia appear as short fine tails.

Reading the descriptions that describe the appearance of some examples are "On the hindwing, there is a broad yellowish discal band and the wing borders are marked with yellowish cilia" is best illustrated in the Yellow Banded Awl (Hasora schoenherr chuza). Or another example like the Chestnut Angle (Odontoptilum angulatum angulatum) whose description reads "Hindwing has elongated tornal cilia" meaning that the hairs on the tornal area of the hindwing is longer than the other cilia on the hindwing.

4. Dentate

The term dentate is used to refer to something as "having teeth or toothlike projections; toothed or notched". E.g. in botany, the term is often used to describe the edges of a leaf as "having a toothed margin". An example of a butterfly's wings featuring a dentate hindwing margin is the Lesser Darkwing (Allotinus unicolor unicolor).

In another example, the description of having a dentate border but where the toothed edge is internal, is the Chocolate Albatross (Appias lyncida vasava), which is often described as having white uppersides with dentate black marginal borders on the fore and hind wings."

5. Falcate

The definition of the word falcate often refers to sickle-shaped or curved edge. In butterflies, the description is often used to describe the edge of the forewing of some species that feature usually pronounced curved termens. Examples of such species are the Chocolate Pansy (Junonia hedonia ida) which has "a falcate forewing".

Another example of a falcate-winged butterfly would be the Common Evening Brown (Melanitis leda leda) whose forewing is prominently curved or sickle-shaped at the outer margin or termen.

6. Hyaline

The descriptor hyaline is defined as "having a glassy, translucent appearance." This anatomical term is often found in the description of the spots in Hesperiidae species (Skippers). These spots, when viewed in a backlight, show that they are translucent as opposed to opaque spots which do not allow the light to shine through.

An example of a skipper's description is the Conjoined Swift (Pelopidas conjunctus conjunctus) which features "pale yellowish-white hyaline spots in spaces 2-4, 6-8 and two cell spots in the forewing."

7. Lunules

Lunules refers to anything crescent-shaped; a crescent-shaped part or mark; a lunula or lune. The etymology is borrowed from the French word lunule which has its origins in the word luna or moon. In butterflies, the anatomical term lunule is often used to describe crescent-shaped spots or markings on the wings of various species. These markings can sometimes be clearly crescent-shaped, or in some cases, vaguely alluding to the curved shaped marking, that may not be so distinct.

An obvious example is the Banded Swallowtail (Papilio demolion demolion) which features a series of pale-greenish sub-marginal lunules on the hindwing. The Knight (Lebadea martha parkeri) is also another species that is described as "the forewing has a series of white post-discal lunules in spaces 2-6, lying on the outer margin of the white discal band."

8. Ocelli

The ocelli (if singular, ocellus), are the eye-like spots on the wings of butterflies. Sometimes they are simply referred to as "eye-spots" to describe these (usually) circular markings on the wings of many species. Ocelli are often used as diagnostic markings to separate lookalike species e.g. in the Mycalesis and Ypthima species.

Many of the larger Satyridae species feature interesting ocelli on their wings. In some Nymphalidae species, like the Junonia spp, these eyespots are believed to form part of their decoy defense markings to make them appear larger or more threatening than they really are.

9. Serrate

To have a serrated edge means to be "notched on the edge like a saw". The word serrate originates from Latin serrātus, equivalent to serr(a) saw. A similar analogy would be an edge or markings that look like a set of sharp teeth.

Examples of serrated markings or serrated wing margins are in the descriptions for the Cethosia spp. like the Malay Lacewing (Cethosia hypsea hypsina) where the "outer margins of both wings are serrated, particularly more so on the hindwings, giving the wings a saw-toothed appearance."

10. Spatulate

The term spatulate means having a "broad rounded end", like a spoon or a spatula. In butterflies, this usually refers to a tail in the Papilionidae species. Descriptions like "has a spatulate tail at vein 4 of the hindwing" highlights the spoon-shaped tail at the hindwing of the butterfly.

Some examples of butterfly species having spatulate tails are the Common Mormon (Papilio polytes romulus), Common Rose (Pachliopta aristolochiae asteris) and Great Helen (Papilio iswara iswara). Note the broad rounded spoon-shaped tails on the hindwing that are characteristic amongst these large swallowtail species.

The spatulate tails of a Great Helen at rest

This sums up the series on anatomical terms for butterflies and it is hoped that this series of articles will help butterfly hobbyists can better understand some of these descriptions when they read these terms in future.

Text by Khew SK : Photos by Khew SK and Horace Tan.

17 November 2018

Butterfly of the Month - November 2018

Butterfly of the Month - November 2018
The Common Awl (Hasora badra badra)

A pristine Common Awl perches on a palm leaf

We are into the second last month of 2018 already! We can feel Christmas round the corner when colourful decorations, twinkling lights and the melodious songs of the season echo through the shopping malls and commercial complexes in Singapore. Websites and media scream of Christmas sales and offers of discounts of the holiday season.

The weather in Singapore has also been rather wet, with particularly extreme heavy rains on some days causing flash floods in various areas. Yet, in spite of the extra effort and engineering interventions by our utilities agency, floods can still happen in Singapore - often emphasising the inevitable outcome of man vs nature, when nature is in no mood to negotiate.

For those of us who travel by air regularly, the recent Lion Air crash with 189 fatalities brings a grim reminder to our over-dependence on technology. The anti-stall function and flight speed indicator had apparently malfunctioned, causing the almost brand new plane to plunge into the sea.

The fantasy world of super-heroes lost its iconic creator, Stan Lee, who passed away at the ripe old age of 95. Those who grew up in the era of comic books, waiting with bated breath for the next issue of Spider Man, Fantastic Four, Iron Man and so on, will appreciate the enjoyment of browsing through the pages of a comic book and fantasising about saving the world with our favourite characters.

A typical pose of the Common Awl, perched upside down beneath a leaf

Coming back to reality, this month's feature butterfly for November 2018 is the Common Awl (Hasora badra badra). This drab, medium-sized skipper can be considered moderately common in Singapore with a distribution across urban parks and nature reserves. It is most often found in mangrove areas where its caterpillar host plant, Derris trifoliata and Derris elliptica grows wild.

The Common Awl flies rapidly amongst heavily-shaded habitats where it is usually found, and is more often seen and photographed perched upside down on the undersides of leaves. When disturbed from its perch, it zips off quickly, and selects another perch under which it will try to conceal itself in its typical upside down position.

A Common Awl feeding at the flowers of a Syzygium tree

The species is known to puddle, particularly on damp organic matter or excretions of birds spattered on the top surfaces of forest vegetation. Other sightings of this species, besides being perched on the undersides of leaves, are when the Syzygium trees bloom. The Common Awl is seen feeding at the nectar-rich flowers together with other butterflies.

A newly eclosed female Common Awl showing the upperside hyaline spots on its forewing

The Common Awl is a drab brown on the upperside with the wings usually unmarked in the male. There may be a series of usually 2-3 small subapical spots on the forewing. The female has three large pale yellow hyaline spots in the discal area of the forewing, with the wing bases ochreous.

A Common Awl feeding on the minerals on the damp surface of a brick wall

The underside is brown, with a purplish glazed sub-marginal band that may appear more pronounced depending on the angle of incident light on the wings. A prominent white spot in the cell on the underside of the hindwing is characteristic of this species. There is usually a white streak at the tornal area of the hindwing.

Two female Common Awls, note the large pale yellow hyaline spots visible on the forewing

Sightings of the Common Awl are usually in the early morning hours before 9am and in the late evenings, when the species is more active. Its crepuscular habit makes the species rather elusive during the normal hours when other butterfly species are up and about. However, along mangrove trails and boardwalks, the Common Awl may be often seen at other times of the day if it is disturbed from its slumber.

Text by Khew SK : Photos by David Chan, Foo JL, Khew SK, Loke PF, Jonathan Soong and Horace Tan

11 November 2018

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 :