19 April 2020

It Takes Two! : Part 1

It Takes Two! : Part 1 
a.k.a. Butterfly Sex!

A mating pair of Leopard Lacewing holding on to a vine

Now that I have caught your attention with the 'S' word, please read on... But before anyone goes off to report this site for featuring undesirable material, let me assure you that this remains a family-friendly blog. Butterflies, like in most species in our animal kingdom, procreation is one of the main objectives of survival, and the need to continue the sustainability of the species line for generations. So perhaps it is a good time to reflect on the birds and the bees, and throw in some butterflies for good measure.

A mating pair of White Kite/Taiwan Tree Nymph (not a native species of Singapore, but can previously be seen at the Sentosa Butterfly Park or the Singapore Zoo)

Unless a species or organism is a hermaphrodite or one that can switch sexes at different stages in their life history for autonomous reproduction, most other species in the animal kingdom is divided by the gender of male or female. We have previously discussed some aspects of butterfly courtship rituals before a successful mating is achieved.

A mating pair of Common Mormons with the female form-polytes above

During this period of global chaos caused by the COVID-19 pandemic and various countries' lock-downs, quarantines and Singapore's own 'circuit breaker' measures, many of us sit at home and try to find ways and means to pass the time. Working, learning and social interaction in the virtual space has become a norm for some of us over the past few weeks. So I spent some time digging out old photos from various archives.

A mating pair of Blue Pansy with the female above

This weekend's blogpost features the work of many accomplished butterfly photographers in Singapore, showcasing mating pairs of butterflies. Whilst I was searching our repositories of butterfly photos from our forums, social media and archives, I was amazed at the number of species that we have photographed of mating butterflies. Very often, skittish species are more cooperative and easier to photograph when they are otherwise distracted by other more pressing activities. And whilst no butterflies were harmed in the photography, some may have thought that we photographers have invaded their privacy!

A mating pair of Clippers (not native in Singapore) but recorded on the Singapore checklist through a single vagrant individual spotted in the wild

However, in admiring these photographs, butterfly observers should also consider the following and take stock of what they can remember when they encounter mating pairs :
  • Obviously, both individuals cannot fly at the same time. Hence, was it the female that was doing all the flying and carrying the weight of both, or was it the male?
  • How far can they fly, considering that they were carrying twice their normal weight?
  • Did they do anything to protect themselves from predation whilst in this vulnerable position?
  • How long did they stay connected? And which of the two that initiated the disengagement? (Butterfly biology suggests that the male has control of the mating process because its claspers hold on to the female and it decides when to release the female. But in the field, is this always the case?)
  • When they stopped to rest on a perch, did their wings remain closed or open?
In this two-part series, we will showcase species from the six families of butterflies and pairs of butterflies caught in flagrante delicto - mostly around various habitats in Singapore. We will start with the largest species in Singapore, from the family Papilionidae (Birdwings and Swallowtails).

Family : Papilionidae

A mating pair of Great Mormon, with the female f-butlerianus at the top

Amongst these spectacular and large butterflies, the females are generally larger, with a greater wing surface area than the males. From many of our mating pair shots, it was also observed that the females did all the flying and carried the weight of both whilst mating. The clues to this observation (besides watching them fly through field observations), are that the female is the one that is perched or holding on to the perch. But these are just generalisations that are not necessarily 100% accurate or validated by research.

From the large Common Birdwing to the Great Mormon and Great Helen, it is observed that the larger female with a greater lift capability carried the pair when mated. For these bigger species, they are more clumsy when flying, and tend to stop more often to conserve their energy. Maneuverability is a challenge as they will knock into leaves and branches when flying, unlike the smaller butterflies.

Mating pairs of Common Jay (left) and Tailed Jay (right)

A mating pair of the Great Helen, with the female on top

For the faster flying and more skittish species like the Graphiums and Papilios it is also usually the females that do the flying for the pair. However, they are harder to photograph, as they tend to continue flying when threatened and are able to fly to higher perches, out of reach of the photographer.

Mating pairs of Common Mormon (left) and Lime Butterfly (right)

Mating pairs of the common urban species like the Lime Butterfly and Common Mormon are also encountered regularly. Usually fast flying and restless, photographing these species becomes less challenging when a mating pair is encountered.

Family : Pieridae

We move next to the family Pieridae (Whites and Sulphurs). The flight speed of the species in this family ranges from very fast to slow. Amongst the fast flyers like the Mottled Emigrant, Striped Albatross and Orange Emigrant, field observations indicate that the males tend to do the flying when the pair is mated. Anecdotal evidence shows that the males choose the perch to rest on, and is the one determining the mobility of the pair, whilst the females tend to remain stationary.

Mating pairs of Mottled Emigrant (top), Striped Albatross (middle) and Orange Emigrant (bottom)

Field observations also show that in some of these species, when a pair is mated, there is often another male trying to elbow in on the action and disturbing the mating pair to break off. However, in most cases, the intruding suitor was unsuccessful in disengaging the mating pair.

Mating pairs of Cabbage White (left) and Psyche (right)

It appears to be the same for the slower flying species in the family, like the Psyche, Cabbage White, Grass Yellows and Painted Jezebel. Due to their relative similarity in size, there is no clear advantage that the females have over the males in terms of the ability to carry the weight of both butterflies when one of them has to do the flying for both.

Family : Nymphalidae Subfamily : Danainae

Mating pair of Plain Tiger with the male at the top

The diversity of species across the different sub-families of these "Brush Footed" butterflies is very wide. Let us start with the sub-family Danainae of Crows and Tigers. These relatively large, slow flying butterflies, particularly the more abundant Plain Tiger, Common Tiger, Black Veined Tiger and the various Glassy Tigers have often been 'captured' whilst mating.

There does not appear to be a consistent pattern of which of the two sexes that does the flying. Although in the handful of cases where I have personally encountered mating pairs, it was the male that tends to do the flying.

Mating pairs of Blue Glassy Tiger (top) and Black Veined Tiger (bottom) with the males holding on to the perch

The presence of key characteristics to separate between the males and females of Danainaes help to determine which of the two sexes is the "dominant" one that does the flying and maneuvering of the pair. In some of my field observations, the male does make attempts to conceal themselves by flying up high, or try to perch amongst branches and leaves that may obstruct any attack on them. However, being distasteful to predators, I wonder why they needed to do that?

Family : Nymphalidae Subfamily : Satyrinae

Mating pairs of Dark Brand Bush Brown (top), Dark Grass Brown (middle) and Burmese Bush Brown (bottom)

Many of the species in this subfamily of Browns and Arguses tend to favour shaded habitats and fly amongst low grasses. Of these, the Bush Browns (Mycalesis) and Rings (Ypthima) are the most often encountered whilst mating. Again, there is no consistency from our observations whether the male or female does the flying when mated. Also, due to their similarity in size and appearance, it is not often easy to distinguish between the pair.

A set of mating pairs of the Common 3, 4 and 5 Rings and Malayan 5 Ring

When mated, many of our photographs depict the mating pair as "equals" - both holding on to the perch they are resting upon. In some of the cases which I have come across, the female did all the flying. However, they are skittish, and tried their best to stay out of sight when intruded upon.

Mating pairs of Common Palmfly (top) and Common Evening Brown (bottom)

Amongst the larger Satyrinaes like the Common Palmfly and the Common Evening Brown, the slightly larger females are the "dominant" species when it comes to the mobility of the pair. They are also quite alert and will try to hide amongst obstacles when disturbed.

Family : Nymphalidae : Subfamilies : Charaxinae, Heliconiinae, Limenitidinae and Nymphalinae

The next group of mating pairs involves species that fall in various subfamilies, ranging from common to rare. In some cases, the sexual dimorphism is very distinct and females may be even 10-20% larger than the males. In these instances, it is quite obvious that the greater lifting power of the larger females gives her the advantage to do the flying for the pair.

A mating pair of Plain Nawab

Species such as the Plain Nawab, whose caterpillars are more often seen in our nature parks and gardens, are rarely seen as a mating pair. The chance encounter of this pair seen at the old Alexandra Hospital Butterfly Trail was the only time I have observed them mating.

Two mating pairs of naturalised exotic species - Leopard Lacewing (left) and Tawny Coster (right)

The Leopard Lacewing, a non-native that has since been naturalised in Singapore, is quite regularly seen mating, particularly in butterfly parks and enclosures. Another exotic, the Tawny Coster, also common in Singapore today, can regularly be encountered as a mating pair in the field. From the many shots of mating pairs posted in forums and social media groups, this is probably the case.

Mating pairs of Burmese Sailor (top), Short Banded Sailor (middle) and Malayan Lascar (bottom)

Amongst the Limenitidinae, the Sailors and Lascars have regularly been spotted mating. These species are usually skittish and difficult to photograph. However, when mating, they continue to be very alert and often fly off to inaccessible perches to continue with their business in privacy.

Mating pairs of Horsfield's Baron (top) and Malay Baron (bottom)

The larger females of the Barons, Dukes and Viscounts, all from the genera Euthalia, Tanaecia and Lexias, the distinctly larger and sexually dimorphic females (in some of the species) make photographing a mating pair quite interesting. The marked difference in the males and females of these genera display the obvious diversity between the sexes.

Mating pairs of Chocolate Pansy (top), Great Eggfly (middle) and Malayan Eggfly (bottom)

This is also similarly observed amongst the Nymphalinae, where the dimorphism and differences in colours, patterns and markings between the males and females are brought out in photographs of mating pairs.

Mating pair of Royal Assyrian

And there you have it, some examples of mating pairs of butterflies. In our next part, we will take a look at the remaining 3 families of butterflies found in Singapore. To all our readers around the world in this current pandemic, stay safe, stay healthy and stay home!

Text by Khew SK : Photos by May Chan, Antonio Giudici, Huang CJ, KhewSK,  Michael Khor, Koh CH, Lim CA, Loh MY,Nelson Ong, Terry Ong, Michael Soh, Horace Tan, Tan BJ, Tea Yi Kai and Anthony Wong