30 March 2019

The Butterfly Legs

The Butterfly Legs
An Anatomical Discussion of the Legs of a Butterfly

A Common Mormon tiptoes on its slender long legs as it puddles on damp sand

Insects form the largest group within the phylum arthropoda. In general, insects have a chitinous exoskeleton, a body that has 3 distinct segments (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Butterflies belong to the Order Lepidoptera (Scaled wings) and are classified as insects.

A Painted Jezebel uses all its six legs to grasp the flower as it feeds on nectar

Fundamentally, this means that all butterflies have six legs. However, even though all six legs are present, the forelegs of some butterfly species have evolved and adapted to perform a totally different function from their original purpose of locomotion (walking). In particular, the species in the family Nymphalidae or often referred to as "Brushfoot" butterflies, have their forelegs reduced to such an extent that they become imperfect and brush-like (hence the name brushfoot) and useless for walking.

A typical butterfly leg has the following five parts, in sequence, from where the leg is attached to the thorax to the extremities (usually the tarsal claws) - coxa, trochanter, femur, tibia and tarsal segments. Butterflies have three pairs of legs - the forelegs (nearest to the head), the middle legs and the hind legs, each attached to a segment of the thorax.

Although each typical leg consists of the standard segmented parts, there is a wide variation of the legs across the butterfly families. This blog article takes a look at some of the differences of the butterfly species' legs from different families. The majority of the photos depicted here are cropped from a full frame DSLR sensor output and may not be as sharp or of high quality as expected.


Papilionidae species have long slender legs that allows the butterfly to "stand tall"

All six legs are present in all the species of the Papilionidae family. A typical Papilionid has the longest legs (measured from coxa to tarsus) compared to the species in other families. The femur of the Papilionid's leg appears more 'muscular' compared to species of other families. The tarsal segments are typically long and when a Papilionid butterfly puddles or uses its legs to hold onto a flower as it feeds, the body of the butterfly is held high and some distance away from the food source.

A Lime Butterfly uses its sharp tarsal claws to grasp its perch as it stops to rest

A Five Bar Swordtail's legs in close up.  Note the greenish hue and sharp spiny hairs on its legs

Most Papiliond species have tibia spurs and the femur, tibia and tarsal segments may be covered with small spiny hairs which aid in holding on to perches and help in gripping onto flowers as the butterfly feeds. The tarsal claws are prominent on all the legs and also help to hold on to branches, leaves and any other perch that the butterfly is resting on.


All Pieridae species have six legs fully developed and functional. Many of the species usually have their legs concolourous with the butterflies' abdomen or wings. There is usually a darker longitudinal stripe throughout the length of the leg. Compared to the Papilionidae, the Pierids have shorter legs. The femur is usually covered with short and soft hairs.

Pieridae have all six legs developed

As with the other species, the Pierids have tarsal claws and fine hairs on the tarsal area of the leg to help it hold on to its perch whilst it stops to rest or when feeding. They usually utilise all six legs to grasp the perch or balance on a flower.


An Autumn Leaf perches with its four legs and balances well with its legs spread out

The Nymphalidae family (or Brushfoots) are unique in that the forelegs of the butterfly species in this family are under-developed and reduced to mere tufts of hair. These 'legs' are therefore are useless and unfunctional. Most of the time, these forelegs cannot be seen, whilst the middle and hindlegs are well developed and robust. The butterfly species in this family appear to have only 4 legs.

A Common Tiger uses its sharp tarsal claws to clutch onto a flower as it feeds on the nectar

A Blue Pansy perched on a flower on its four legs.  Note the sharp spiny hairs on its legs

The variety of species in the sub-families Danainae, Satyrinae, Nymphalinae and so on clearly show that they are not in any way disadvantaged with only 4 legs. They go about their usual daily routine using just the remaining 4 legs (middle and hind legs) without any problems at all.


A Female Harlequin has all six legs developed.

The Riodinids are unique in that only the females have six fully developed legs. In the males, the forelegs are reduced to tufts of hair like in the Nymphalidae and these legs are not functional. However, the females tend to fold their forelegs tightly to the front of the thorax and appear to also have only 4 legs to stand on.

A male Harlequin has four developed legs whilst its forelegs are reduced to just tufts of hair

The legs of the Riodinids are relatively short and thick with the tarsal segments, particularly at the extremities close together giving them a banded appearance. The legs of the Riodinids also appear to lack the prominent tibia spur that can be found in other species of butterflies.


A Blue Brownwing's unique shaped legs. Note the compressed tarsal segments of its foreleg

A Bigg's Brownwing with its rather specialised foreleg that appears spatulate and flat

The variety of leg designs across the many genera of Lycaenidae is quite amazing. Of special note are the legs of some species of sub-family Miletinae. Of interest are the legs of the Miletus spp. The legs appear flattened and taper towards the joints. The tarsal are broader towards the extremities and as least in one of the species, the forelegs appear to lack the tarsal claws.

A variety of six-legged Theclinae with banded and pure white legs

In other species of the subfamily Theclinae, the legs are short and thick, and may sometimes be black and white banded. In other species, all six legs appear as if they are clad in white stockings. The tibia spur occur in many species across the family and the tarsus is also covered with small spiny hairs which allow the butterfly to hold on to its perch firmly.


Note the exceptionally hairy femur and tibia of some Hesperiidae species

The Skippers have all six legs fully developed. In many of the species, the femur is exceptionally hairy and covered with thick long hairs, giving this segment of the leg a rather thick and muscular appearance. In some species, the hairs extend to the next segment, the tibia. The tibia spurs are thick and prominent. On the hind legs, there is usually an additional pair of tibia spurs in a number of species.

The White Banded Flat has evolved a rather strange tuft of hair on the tibia of its hind legs

In some unique species, like the White Banded Flat, the hind legs are further evolved to have a prominent hair tuft covering the tibia and extending beyond the leg.

So the next time you have an opportunity to observe a butterfly closely, take a look at its legs and see what interesting observations you can make about the legs of different species of butterflies.

Text by Khew SK : Photos by Huang CJ and Khew SK

23 March 2019

Three Archdukes

Three Archdukes
Singapore's Archduke butterfly species

A male Archduke foraging amongst the leaf litter in the shaded forest understorey

In my earlier article on this blog, I postulated that the English common naming convention of butterflies could have been possibly coined after the titles of English peerage or Imperial gentry and military ranks. In this article, we take a look at the Archduke butterfly species that can be found in Singapore.

A female Dark Archduke on leaf litter 

Unlike the English peerage titles, the Archduke (feminine: Archduchess) was a title that originated from the Habsburg rulers of the Archduchy of Austria. It denotes a rank within the former Holy Roman Empire, which sat just below that of Emperor and King.

Hierarchy of titles in Imperial, royal, noble, gentry and chivalric ranks © Wikipedia

The etymology of the word Archduke originates from various European languages and purportedly signifies authority or primary (Arch) and leader (Duke). Notwithstanding the historical origins of the royalty-linked name, the Archduke butterflies are no less majestic in their size and prominence in the butterfly world, befitting of their common name.

A Yellow Archduke perches on a leaf in the forested nature reserves

There are 3 extant species of Archdukes that can be found in Singapore. Belonging to the genus Lexias, which features large, robust-bodied and fast-flying butterflies that prefer the heavily shaded forests rather than open sunny areas. All are considered forest-dependent and not found in urban parks and gardens. They are usually found foraging for over-ripened fruits and feeding amongst the leaf litter on forest paths.

The Archduke (Lexias pardalis dirteana)

Upperside and underside of a male Archduke

The commonest species of the genus, the Archduke displays sexual dimorphism in that the male is physically very different from the female. The male is dark velvety black above with a broad blue hindwing border, which is continued (usually in a lighter shade) along the termen of the forewing. The underside is a deep reddish brown with yellow spots.

Upperside and underside of a female Archduke

The female is dark brown above, with prominent yellow spots on both wings, including the body of the butterfly. The underside is a light brown with the yellow spots showing through. The hindwing is a pale-greyish blue throughout.

Note the bright orange apical tip of the Archdukes' antennae

In both sexes, the apical portion on the topside of the antennae is prominently orange. The orange colour is continued on the underside of the antennae as well. This is the most reliable distinguishing characteristic that separates the Archduke from its very closely related Dark Archduke.

The Dark Archduke (Lexias dirtea merguia)

A male Dark Archduke on leaf litter

Almost identical to the Archduke, the Dark Archduke (previously called the Dark-Tipped Archduke), is also sexually dimorphic, with the male and female's appearance corresponding to the Archduke. The habit of this species mirrors the Archduke, and individuals are often found feeding on rotting fruit and other organic matter amongst leaf litter on the forest floor.

Upperside and underside of a female Dark Archduke

The male and female of the Dark Archduke closely resemble the corresponding sexes of the Archduke. The male is velvety black above with the blue marginal border on the hindwing, which extends to the termen of the forewing. The female is dark brown with yellow spots on both wings.

Note the black antennal tips of the Dark Archduke male and female

The primary difference between the Archduke and Dark Archduke is that the apical portion of the antennal club is black instead of orange. The underside of the antennae can still show some orange colouration like the Archduke. It is almost impossible to distinguish the two species when in flight, although there are some key, but still variable differences on the wings of both species to help distinguish them.

The Yellow Archduke (Lexias canescens pardalina)

Yellow Archduke puddling on the forest floor

The third, and smallest species of the three Archdukes is the Yellow Archduke. Of great interest is that it is the only species in the Lexias genus that is not sexually dimorphic! Both the male and female look alike, although the female is usually much larger. Displaying the same forest-floor foraging habits as its two other cousins, it is also a forest-dependent species.

Upperside and underside of the Yellow Archduke

The Yellow Archduke is dark brown above with large yellow spots on both wings, resembling the females of the Archduke and Dark Archduke. However, both the males and females look alike. The underside of the hindwing only has the dorsal margin a pale-greyish blue with the larger part of the wing brown and yellow.

Mating pair of the Yellow Archduke

On the upperside of the forewing, the line of yellow spots at the post-basal area features a spot (the 4th spot from the base) which is coalesced into a single spot. In the female Archduke and Dark Archduke, this yellow spot is split into two spots. This is the most reliable characteristic to separate the Yellow Archduke from its two close cousins.

Text by Khew SK : Photos by Khew SK, Koh CH, Nelson Ong, Simon Sng and Jonathan Soong

17 March 2019

Assorted Nectaring Plants - Part 4

Butterflies' Nectaring Plants
Assorted Flowering Plants - Part 4

A Blue Glassy Tiger feeding on the flower of the Belimbing (Averrhoa belimbi)

We are back with a selection of another six flowering nectar plants that butterflies visit for their source of energy to go about their daily activities. These plants, on the other hand, have adapted their reproductive parts to suit their pollinators e.g. bees, butterflies, moths, etc., to ensure the continual survival of their species. As most people would know, in the process of feeding on the nectar from these flowers, butterflies help to pollinate the plant which enables fertilisation and the production of seeds for the next generation of the plant.

A Dark Glassy Tiger feeding on the yellow flower of the Pig's Grass (Synedrella nodiflora)

Butterfly-plant relationships are not limited to their caterpillars that feed on their specific host plants. Adult butterflies have a preference for different types of flowering plants for their nectar source. Whilst many butterflies have their preferred or favourite flowers, this series of assorted flowering plants showcases various other types of flowers that butterflies occasionally visit for their daily liquid diet.

19. Bougainvillea (Bougainvillea glabra) hybrids

Colourful bracts of the Bougainvillea makes it a popular landscaping plant.

This attractive flowering plant is almost synonymous with the urban landscape of Singapore - from the time a visitor arrives at Changi Airport and takes a drive down the tree-lined East Coast Expressway into town. The colourful bracts of the Bougainvillea comes in many colours from white and yellow to pink and red. They adorn roadside verges, overhead bridge planters and are commonly seen as a decorative plant in public and private gardens.

Despite its showy colourful bracts, the actual flowers from which butterflies extract nectar are small and insignificant. These flowers are creamy-white, tubular and inconspicuous. Although the plant is common all over Singapore, butterflies are rarely attracted to the flowers for nectar. Only occasionally are butterflies observed to feed on the flowers for nectar.

A Tree Flitter probes deep into the tubular flower of the Bougainvillea

I have observed urban species like the Painted Jezebel, a couple of Glassy Tigers and some Swallowtails visiting the flowers for a quick re-fuelling stop, but they do not stay for long, or flutter from flower to flower on the plant to feed, unlike many of the other favourite nectaring plants. In the nature reserves, the occasional Skipper (Hesperiidae) are encountered feeding on the Bougainvillea flower in the early morning hours.

20. Pig's Grass (Synedrella nodiflora)

A Suffused Flash feeding on the flower of the Pig's Grass

This herbaceous plant can grow up to about 1-2m high and can be found along roadsides and wastelands. It appears to be more common in the backmangrove areas like Sg Buloh Wetland Reserves and Pulau Ubin. The small yellow flowers can sometimes be mistaken for the more common creeper, the Singapore Daisy (Sphagneticola trilobata) which belongs to the same Asteraceae family as the Pig's Grass.

A Spotted Black Crow feeds in the yellow flower of the Pig's Grass

The yellow ray florets attract a number of Danainae like the Glassy Tigers and some of the Crows. At Sg Buloh, we have observed some Lycaenidae like the Suffused Flash and Singapore Four Line Blue feeding on the yellow flowers. The primary pollinator of this plant appears to be bees and wasps, and they are more often seen on the flowers than butterflies.

21. Malayan Eyebright (Legazpia polygonoides)

A Plain Lacewing feeding on the flower of the Malayan Eyebright

This slender herb is classified under the Torenia family, which comprises low ground creeping weeds that grow amongst the grass in open gardens and landscaped lawns. The leaves are small, rounded with toothed edges. The plant flowers frequently. The small flower has a lower white lip of three lobes, and upper lip of red. The centre is tinged with yellow.

The small unique flower of the Malayan Eyebright contains nectar which some butterflies feed on

The diminutive flowers usually attract the smaller butterflies in the Lycaenidae and Hesperiidae families, but the Grass Yellows and Tree Yellow have been observed to stop and feed on the flowers as well. It was a surprising observation when the rare and elusive Plain Lacewing (Cethosia methypsea methypsea) was photographed feeding on the flowers of the Malayan Eyebright in the early morning hours.

22. Belimbing (Averrhoa bilimbi)

A Blue Glassy Tiger feeding on the pretty red flower of the Belimbing

This medium-sized tree can grow from 5-10m tall. Originating from Southeast Asia, the Belimbing is known for its very sour fruits that are used as a relish or garnishing in local cuisine. It is also closely related to its more well-known cousin, the Starfruit (Averrhoa carambola). A unique feature of the Averrhoa plants is that they flower and fruit directly on their trunks and branches.

The flowers and fruits of the Belimbing growing off the branches of the tree

A Common Grass Yellow feeding on the flower of the Belimbing

The flowers are small purplish-red, borne in a pendulous panicle inflorescence. Each flower is 5-petaled and fragrant, and each inflorescence has about 60 flowers, usually growing off the trunk or branches of the tree. Occasionally, the flowers attract butterflies like the Glassy Tigers and Grass Yellows. I have not yet recorded any other species of butterflies feeding on the flowers.

23. Common Vernonia (Cyanthillium cinereum)

A Lesser Grass Blue feeding on the flower of the Common Vernonia

Previously known as Vernonia cinerea, this wild-growing weed usually found along roadside green verges, open wastelands and even cracks in the joints of paved concrete footpaths. It grows as a small herb and the stalks of the flowers grow upwards with several flower heads on a single stalk. The purplish to white flowers comprise fine disc florets to which small butterflies are attracted.

Various species of the Grass Blues like the flowers of the Common Vernonia as a nectaring source

Due to its very small size, this wildflower attracts the smaller Lycaenidae like the Lesser Grass Blue and the Pale Grass Blue. It is highly unlikely that any of the larger butterflies can feed on the Common Vernonia as it is 'designed' for only the very fine and small diameter proboscis of small butterflies that are able to feed on it.

24. False Heather (Cuphea hyssopifolia)

A Metallic Caerulean feeding on the flower of the False Heather

This low-growing shrub with fine leaves are often used in landscaping as a border plant to line footpaths or planters. The bright green leaves are opposite and pointed. A native of South America, the False Heather was probably introduced to Singapore as an ornamental plant used in cultivated landscaped gardens.

A Yellow Grass Dart feeding on the flower of the False Heather

The small purple flowers occasionally attract butterflies to feed on them when there is a shortage of other more popular nectar-laden flowering plants are not available. Amongst the species that have been observed to visit the flowers for nectar are Striped Albatross, the Grass Yellows, and other small Lycaenidae and Hesperiidae species.

Text by Khew SK : Photos by Chng CK and Khew SK

Assorted Nectaring Plants - Part 1
Assorted Nectaring Plants - Part 2
Assorted Nectaring Plants - Part 3