Tawny coster Acraea terpsicore. Photo by Green Baron Pro on Flickr. Creative Commons.
The Tawny Coster, Acraea terpsicore belongs to the largest family of butterflies Nymphalidae 1 . Butterflies of family Nymphalidae are commonly known as four-footed butterflies as most species are known to stand on four legs with the another pair curled up2 . This species is introduced to Singapore 3 . In September 2006, tawny coster was first discovered in Singapore at an open wasteland in the north-eastern part of Singapore. Since then, it has spread to many other parts of Singapore and is now a commonly seen butterfly all over Singapore, including the offshore island of Pulau Ubin4 . The rapid spreading Tawny Coster is suspected to be a potential invasive species. Please visit Section 1.1 The Journey of the Tawny Coster and Section 2.7 Conservation Status for more information regarding its spread and potential invasive status.
Glasswing Butterfly Greta oto from family Nymphalidae standing on four legs. Photo by William Warby from Flickr. Creative Commons.
1.1 The Journey of the Tawny Coster
This species occurs naturally in grasslands and scrub jungles of peninsular India and Sri Lanka5 . However, it has spread to South-East Asia during the past three decades. It has become widely established in the northern part of South-east Asia5 . The first sighting of Tawny Coster was detected in Lombok Indonesia, Timor and Australia in 2012 6 5 . From the figure below, it can be observed that Tawny Coster has been travelling down South, from Sri Lanka and India to the further south South-East Asia and then Australia. Please visit Section 2.6 Global Distribution for its distribution worldwide.
Distribution of tawny coster in South-East Asia and north-western Australia, showing known locations (black circles). Years of detection (first recordings) are indicated for each country. Image adapted from journal by Braby et al 2014.
While there have been competing hypotheses regarding the establishment of Tawny Coster in South-east Asia, Braby et al 2014 have postulated three hypotheses on its establishment5
1. Tawny coster was accidentally and recently introduced to Indo-China from India/Sri Lanka
2. Tawny coster naturally expanded its range out of India and colonised Thailand via Myanmar
3. Tawny coster always existed in the region (Thailand and Vietnam), but has since become more abundant and widespread as a result of modification in the environment through agriculture, the butterfly favouring cultivated regions and degraded forests where the larval food plants grow.
A separate news article interviewing Dr Braby revealed a likely reason behind its establishment in South-East Asia. He revealed that tawny coster is not introduced by humans unlike many invasive species. Instead, it is speculated that human activity is the reason behind its rapid spread. Tawny coster breeds on plants that thrive in disturbed habitats7 . With tropical forests in South-East Asia experiencing major deforestation, these host plants thrive 8 . Along with the chemical defense 'immunity' tawny coster has developed, these could have contributed to the range expansion of the tawny coster. Please visit Section 2.4 Defense for more information regarding its chemical defense.
1.1.1 Local Distribution
Local Distribution of tawny coster.
The genus name Acraea is derived from the ancient Greek word acraeus which means at high latitude9 . However, and strangely enough, tawny coster is in fact a lowland species5 . The species name terpsicore is derived from the Greek word Terpsichorē, which refers to the Greek Muse of dancing and choral song, likely a reference to the lazy sailing dance-like fluttering of the tawny coster10 . The common name Tawny refers to the tawny coloured wings of the tawny coster accompanied with black spots on them.
Dance-like fluttering of tawny coster. GIF adapted from Youtube video by Henrik Bloch.
Tawny coster is a medium-sized butterfly with the wingspan of an adult butterfly ranging from 48mm to 54mm 11 . The upperside is deep orange with narrow, black outer borders and black wing spots 12 . The black thorax and black hindwing border are spotted white. The underside is paler with markings more prominent.
Deep orange upperside of tawny coster (left). Photo by Patrick Peter on Flickr. Creative Commons. Paler orange underside of tawny coster (right). Photo by Sandeep Somasekharan on Flickr. Creative Commons.
2.1 Local Host Plants
The local caterpillar host plants are mainly from family Passifloraceae13
. They include the following:
|Scientific names||Common names||Family||Local status||Host plants for other butterflies found in Singapore|
|Passiflora foetida||Stinking passionflower, love-in-a-mist||Passifloraceae||Non-native||Cethosia cyane Leopard Lacewing (non-native)|
Dryas iulia Julia Heliconian (non-native)
|Passiflora suberosa||Corky-stemmed passion flower||Passifloraceae||Non-native||Dryas iulia Julia Heliconian (non-native)|
|Passiflora edulis||Passion fruit||Passifloraceae||Non-native|
|Turnera ulmifolia||Yellow Alder||Turneraceae||Non-native|
Passiflora foetida, stinking passionflower, in particular is a naturalised common weed in our wastelands, cleared areas and along roadsides, and is the favourite host plant of the tawny coster14
. It is a fast-growing vine, able to smother other plants within a short period of time16
. The stinking passionflower uses its clinging tendrils to climb over other plants and is able to easily overtake other plants, shading them from the sun. With its ability to overtake other plants, it grows in relative abundance in the disturbed habitats. This may explain the rapid spread of tawny coster across the island, after it first appeared in Singapore since 2006.
Stinking passionflower. Photos by Horace Tan, permission granted.
Adults of tawny coster can usually be sighted visiting the flowers of stinking passionflower for the nectar while the caterpillars feed on the leaves, young shoots, tendrils and outer surface of the young stems.
Similar to the stinking passionflower, the other host plants are fast-growers that are able to smoother other plants, thus may also explain the spread of tawny coster across the island18 .
2.2 Life Cycle
|Oviposition (Depositing of eggs)|
Female tawny coster oviposits on the underside of stinking passionflower.
The eggs are yellow in colour and olive-shaped.
The infant caterpillar consumes the upper portion of the egg shell while hatching.
The body segments develop a bright yellowish brown coloration. This instar lasts about 2 to 2.5 days.
Body turns orangy brown. This instar lasts 2 to 3 days.
Similar physical appearance as 2nd instar. This instar lasts 2 to 3 days.
Similar physical appearance as 3rd instar, except for paler coloration in first two segments. This instar lasts 3 to 5 days.
Little change to physical appearance except for the increase in size. This instar lasts 5 to 7 days.
|6th and final instar|
Head turning almost fully orange. This instar lasts between 9 to 13 days.
Pupation takes place on the underside of the stem. White-based pupa has black narrow bands running lengthwise. This lasts for 5 days before the pupa matures and turns salmon orange.
Eclosion takes place one day after the pupa turns salmon orange.
Tawny coster adult butterfly emerges from its pupal case. Original video from YouTube by Horace Tan
2.3 Sexual Dimorphism
Sexual dimorphism is the difference in morphology (physical appearance) between the male and female. It includes differences in size, coloration or body structures20
The wings of the male are deep salmon orange (left) while the wings of the female are pale tawny yellow (right). Photo by paper from Braby et al. Permission pending.
Aposematism is a defense strategy adopted by species that warns potential predators of their unpalatability21
. These species usually have conspicuous colour patterns, and potential predators will learn to associate these bright colouration to unpalatability of the species thus escaping predation. The predators thus learn from the experience and avoid any similar looking preys in the future.
In the animal kingdom, the typical warning colours are black, yellow, red and orange 22 . Many butterflies that exhibit aposematic colouration come from the families Papilionidae and Pieridae, and subfamilies Danainae and Heliconiinae. Subfamily Heliconiinae, the subfamily which A. terpsicore belongs to, derive their unpalatability as caterpillars when they feed on Passifloraceae 23 . The caterpillars are able to sequester the toxins present in their Passifloraceae host plants which are then retained in the adult stage. The adults then secrete a foul smelling yellow oily fluid from their glands in leg joints when they are being attacked, making them unpalatable to the predators21 . This mechanism thus protects butterflies from subfamily Heliconiinae from potential insectivorous predators such as birds.
Altinote dicaeus callianira from Family Nymphalidae (left). Photo by Andrew Nield from Flickr. Creative Commons. Danaus plexippusMonarch Butterfly from subfamily Danainae (right). Photo by John Flannery from Flickr. Creative Commons.
Distasteful to predators, tawny coster is avoided by birds and most of the insects. Some mantises and lizards are noted to predate on the tawny coster.
Tawny coster caught by mantis at Coney Island. Photo by Sandy Tan
In the animal kingdom, females are usually the higher investing sex and may have multiple mating partners24
. Females are the higher parental investment mates as they support the weight of the many relatively heavy-weight eggs before fertilisation, and after fertilisation, dedicate to taking care of the offspring. Thus as the higher parental investment mates, the females can be choosy about their mates, as the quality of her offspring is dependent on the quality of her mate. This is commonly as known as female mate selection. One popular example is in frogs, where female frogs tend to be attracted to the males with the loudest and most distinctive acoustic display of their mating calls. Via the mating calls, the females would gain signals on the quality of the males, then select the male that would offer the highest in return for mating. In butterflies, female mate choice is dependent on both visual and olfactory cues25
. Mate recognition is performed via visual cues, while olfactory scents are emitted by male butterflies to court the females in close range26
So... does it mean that the fate of the paternity solely depends on the female's choice? NO!!
Sphragis on the female copulatory opening. Photo and annotation by Horace Tan. Permission obtained (left). Dorsal view of sphragis. Annotations by Sandy Tan. Photo from paper by Braby et al (middle) Permission pending. Lateral view of sphragis. Photo from paper by Braby et al (right). Permission pending.
With females being choosy with their mates, there exists high male-male competition as they compete for access to mating. Thus males have also evolved adaptations to increase males' chance of reproductive success27 . Males can do so by post-copulatory sperm competition. One example of post-copulatory sperm compeition is the sphragis.
Male butterflies utilize a mechanical tactic known as the sphragis, mating plug or copulatory plug to reduce female re-mating tendencies to cope with sperm competition28 . Sphragis is a glandular, waxy secretion which is passed along with the spermatophore (sperm packet). As female butterflies have two genital openings, the sphragis covers the female's copulatory opening without obstructing oviposition. This waxy secretion hardens within hours of copulation to prevent further mating of the females. The sphragis thus serves as a mechanical barrier to reinsemination of the female butterflies.
However, the effectiveness of sphragis in tawny coster is uncertain. In a study on the function of sphragis in the Chalcedon Checkerspot Butterfly Euphydryas chalcedona, belonging to Family Nymphalidae, it was discovered that sphragis does indeed prevent reinsemination 29 . The presence of sphragis did reduce the copulatory success of males courting the females by preventing intromission. In tawny coster, sphragis have been sighted on the mated females. However it remains unclear whether females do mate multiple times in the first place, or if the presence of sphragis do prevent reinsemination in tawny coster.
2.6 Global Distribution
Global Distribution of tawny coster. Blue markers indicate current distribution. Red markers indicate potential range expansion predicted by Braby et al 2014.
2.7 Conservation Status
Tawny coster has not yet been assessed for the IUCN Red List30
. However, from its rapid spread, it seems unlikely that tawny coster would be facing any threat in the near future.
The question better suited for tawny coster should be: Could tawny coster potentially be an invasive species since its host plant stinking passionflower is also spreading rapidly in Singapore?
The biological and economical impacts of tawny coster has yet to be studied, however, in Sri Lanka where this species is native in, tawny coster is infamous for being a pest for local market gardeners, destroying the harvest of various gourds of Family Cucurbitaceae5 . Locally in Singapore, the relative abundance of P. foetidacould be an explanation behind the rapid spread of tawny coster in Singapore. With an abundance of the host plant, the population of tawny coster is able to flourish as well.
A personal observation at Coney Island: There is an increase in spread of stinking passionflower (major host plant for tawny coster) in Coney Island to an extent that it seems to be growing at areas where Cynanchum ovalifolium Akar Bano was usually found to be present at. As a result, sightings of Danaus genutia genutiaCommon Tiger seemed to have lessened. Could it be that the spread of stinking passionflower could have indirectly resulted in the displacement of common tiger butterfly?
Common tiger (left). Photo by Sek Keung Lo from Flickr. Creative Commons. Akar bano (right) Photo by Horace Tan. Permission obtained.
3 Taxonomy and Systematics
There have been no subspecies listed under this species.
3.2 Original Linnaean Description
Original Linnaean description in Systema Naturae (1758).
Linnaeus described A. terpsicore as having oblong spotless yellow wings with its rear saturated with scattered black spots31 .
|Danaus chrysippus chrysippus|
|Danaus genutia genutia|
Papilio terpsicore Linnaeus, 1758 is the oldest available name of this species 34
. The species was subsequently moved to a different genus Acraea and is named Acraea terpsicore (Linneaus, 1758).
Papilio violae Fabricius, 1775
Papilio cephea Cramer, 1780
Acraea violae (Fabricius, 1793)
There has been much confusion over the identity of this species as many authors pointed out that the Linnean type material used to describe this species has not been located35 . It was then discovered that the type of tepsicore Linnaeus existed in the collections of the Linnean Society of London and identified as such36 . The type of violae Fabricius is in the Zoological Museum, Copenhagen 34 .
As Papilio terpsicore Linnaeus, 1758 is the oldest available name, it is therefore a senior synonym of Papilio violae Fabricius, 1775.
Specimen of terpsicore in Linnean Society of London (left) Image from Linnean Society of London. Specimen of violae in Zoological Museum, Copenhagen (right) Image from paper by Honey and Scoble 200134 .
Until now, there have been uncertainties regarding the scientific names of the Tawny Coster. Some online pages refer Tawny Coster to A. violae while others refer it as A. terpsicore.
Butterfly circle, a butterfly enthusiast group in Singapore have been using A. violae to describe Tawny Coster but since 2015, the scientific name of this species has been adopted as A. terpsicore.
Adopting A. terpsicore as scientific name. Image taken from Butterfly Circle 37 .
The brush-footed butterflies (Nymphalidae) belongs to superfamily Papilionoidea. This superfamily consists of all the true butterflies of five families - Papilionidae, Pieridae, Nymphalidae, Riodinidae and Lycaenidae. An estimation of 13 700 species of true butterflies are extant in the world 38 .
Cladogram of the true butterflies. Image from Tree of Life web project.
The subfamily Heliconiinae was recently divided into 4 tribes - Acraeini, Heliconiini, Vagrantini and Argynnini 39 . A. terpsicore belongs to the tribe Acraeini. Acraeini is thought to comprise between one and seven genera distributed in the Neotropics and Old World 40 .
Division of subfamily Heliconiinae into 4 tribes. Image from Nymphalidae.net
Phylogenetic analyses were conducted based on both molecular and morphological data. The molecular sequence data were based on 2 nuclear gene region (EF-1a and Wingless) and 1 mitochondrial gene region (COI). The morphological data matrix involved a total of 99 characters, with 95 characters scored from adult butterflies, and 4 characters scored from immature stages41 .
Phylogenetic analyses of the combined molecular and morphological datasets. (a) Single most parsimonous tree. Numbers above the branches are Bootstrap value for the node to the right of the numbers and italicized numbers below branches are node numbers. (b) Tree resulting from Bayesian analysis using mixed models. Number below branches are posterior probabilities for the node to the right of each number. Colour codes represent families as follows: pink, Hedylidae; red, Hesperiidae; green, Papilionidae; yellow, Pieridae; purple, Riodinidae; blue, Lycaenidae; orange, Nymphalidae. Annotation from Sandy Tan. Screenshot taken from study by Wahlberg et al.
The analyses of the combined molecular and morphology dataset provide strong support for the monophyly of all traditionally recognised higher taxa. However Nymphalidae (family of the tawny coster) was an exception with moderate Bremer support (6), high posterior probability (100%) but no bootstrap support (less than 50%). Characters (morphology, COI and EF-1a) do support the monophyly of the family however Wingless conflicts moderately, which resulted in the above phylogenetic tree. A postulation regarding the unsupported monophyly of Nymphalidae is that the major lineages diverged very rapidly from one another. The uniquely derived features used to define the family is thus a challenge.
4.1 DNA Barcode
The DNA Barcode data for this species can be found here.
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This page was authored by Tan Tze Min Sandy
Last curated on 2016