29 April 2018

Sexual Dimorphism : Part 1

Sexual Dimorphism in Butterflies : Part 1
Featuring Male-Female Differences

A mating pair of Orange Emigrant.  Left : Male, Right : Female

Sexual dimorphism in butterflies is the condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs. These differences may include size, colour, distinguishing markings and secondary characteristics. In some cases the flight characteristics between the males and females are also distinctly different. The differences in sexual dimorphism can range from negligible to exaggerated, and may be subjected to sexual selection.

The degree of differences in sexual dimorphism in butterflies can be classified under a range that falls between negligible to exaggerated. I have further broadly categorised the differences into the following 4 categories :
1) Negligible : Males and Females appear so similar that it takes a bit more effort to scrutinise secondary characteristics closely to ascertain and differentiate between the males and females.
2) Subtle : Males and Females appear similar but there are minor giveaways that can instantly distinguish between the males and females
3) Distinct : There are clear differences between males and females that a glance will be able to separate between the two sexes in these species.
4) Exaggerated : The males and females of these species of butterflies appear so different that one could even assume that they are two different species.

A mating pair of Dark Brand Bush Brown.  Left : Female, Right : Male

These categorisations are by no means scientifically based and not intended as formal scientific classifications. As in any general layman categorisations, they are based on personal observations and there are certainly outliers and exceptions that may or may not fall clearly into any of these categories.

A mating pair of Pale Mottle

Then there are examples of dorsal and/or ventral sexual dimorphism. This is where the differences between males and females of a species are either on the dorsal (upperside) or ventral (underside) of the wings. In some cases, the differences are both on the dorsal and ventral sides of the wings.

A mating pair of two different morphs of the Lemon Emigrant

In some exceptional species, the sexual dimorphism is further expanded to polymorphism (i.e. more than just one form in either sex). This phenomenon may occur in just the females that display many different forms, or just the males that display many different forms. And then in some extreme examples, both the males and females display polymorphism. But by and large, only a handful of species fall into these categories. In Singapore, some examples are the Great Mormon, Malay Baron and Lemon Emigrant.

1 . Sexual Dimorphism (Negligible differences)

A pair of Lime Butterfly.  With a close look at the abdominal tips of the two individuals, it can be ascertained that the female is the top butterfly and the male is at the bottom

We now take a look at some of the examples of butterflies that fall into the 4 broad categories of sexual dimorphism. The first category is the most straightforward - where the males and females of a butterfly species are physically similar and it may take careful scrutiny to establish between a male and female of the butterfly. Examples shown here are certainly not exhaustive but just to illustrate some species that fall into this category.

Top : Male Lime Butterfly Bottom : Female Lime Butterfly. Note the size of the tornal spot and proportion of the blue-edged black spot to the red spot

Our first examples from the Papilionidae family would be the Lime Butterfly (Papilio demoleus malayanus). Ventrally (or seen from the underside), this species' sexual dimorphism can be considered 'negligible'. On the dorsal (upperside) of the wings however, the dimorphism may be considered 'subtle' as the main difference between the male and female of this species is the tornal spot on the hindwing. In space 1b on the hindwing, there is a red spot in both sexes. In the male, this spot is capped with a narrow blue lunule with a very narrow intervening black gap. In contrast, the red spot and the blue lunule in the female have a rather large black spot between them.

A mating pair of Psyche.  Difficult to separate between male and female from the underside

An example from the family Pieridae would be the Psyche (Leptosia nina malayana), in which the male and female are virtually indistiguishable when viewed from both the upperside and underside of the wings. The mottled underside and the predominantly white upperside with a black apical patch and a black spot on the forewing is almost identical in both the male and female of this species. This makes it near impossible to separate between the male and female of this species unless the primary sexual organs are examined.

From the Nymphalidae family, a good example of negligible difference in sexual dimorphism would be the Peacock Pansy (Junonia almana javana). This pair of mating Peacock Pansy demonstrates that there is almost little or no perceptible dimorphism between the male and female of this species. When viewed ventrally, it is difficult to separate the two. The two sexes are also near identical on the upperside with the usual ocelli present in both the male and female.

This pair of Common Caerulean (Jamides celeno aelianus) represents an example of negligible difference category as far as sexual dimorphism is concerned. Ventrally, the male and female is difficult to set apart from just the physical markings on the underside of the species. However, on the dorsal side, the sexes can be distinguished by the broader black border on the forewings of the female, making this species a dorsally distinct category.

Mating pairs of Skippers showing very indistinct differences between the males and females

Amongst the skippers, there is less sexual dimorphism in quite a number of the species in the family Hesperiidae. Quite a large number of the species can be classified under the negligible difference category. Examples shown here are the Large Snow Flat (from the sub-family Pyrginae), the Chestnut Bob and Grass Demon (from the sub-family Hesperiinae).

2. Sexual Dimorphism (Subtle differences)

Mating pair of Tailed Jay.  Female is the one on top, with its comparatively longer tail

The next category would be butterflies that demonstrate subtle differences in males and females of a species. The degree to which we can consider the "subtleness" in the difference between a male and female of butterflies is rather subjective, and here, we just give examples where there are minor features that are able to give away the difference between the sexes.

Left : Male Tailed Jay and Right : Female Tailed Jay.  Note the comparative length of the tails

A Papilionidae example of subtle difference between the male and female of the species is probably the Tailed Jay (Graphium agamemnon agamemnon). In this species, the key difference between the sexes is the relative length of the tail of the butterfly. Whilst the colour, spots and size are usually similar (with the male typically slightly smaller), the individual with the longer tail (usually twice as long) is the female. This very subtle difference separates the male from the female of this species.

Mating pair of Orange Emigrant.  The female, on the right, has darker and more pronounced spots on the wings

A typical example of a Pieridae that displays subtle differences between the male and female would be the Orange Emigrant (Catopsilia scylla cornelia). In the photograph shown of a mating pair, the female has more spots on the hindwings compared to the male, and on the dorsal side, the female has a black marginal border on the hindwing (absent in the male).

Mating pair of Plain Tiger.  The male, on the top, has an extra spot on the hindwing

From the subfamily Danainae, the secondary sexual characteristics of a sex brand on the hindwings is a subtle diagnostic feature that separates the male from the female. In the case of this mating pair of Plain Tigers (Danaus chrysippus chrysippus), the male (top) has an additional "spot" in the form of a sex brand on the hindwing. The female does not have this brand. This subtle spot separates the sexes in this species.

Mating pair of Apefly.  The female, on the left, has a more rounded forewing compared to the sharper and more angular shape of the male's forewing.

In this pair of Apefly (Spalgis epius epius), the structure of the wings is a very subtle giveaway in separating the male and female butterflies. The forewing of the male is more pointed and pronounced compared to the more rounded forewing of the (usually) larger female. The male, on the right of this photo, displays the more angular forewing and is obvious enough to distinguish between the sexes.

A mating pair of Common Mormon with clearly distinct features between the male and female.  These two categories will be discussed in Part 2 of this article next week.

In Part 2 of this article, we take a look at species with more distinct physical appearances between the males and females. We also look at the evolution of some of these examples of sexual dimorphism and ask some questions with regard to some of the reasons behind some of these evolutionary adaptations, probably by natural selection.

Text by Khew SK : Photos by Chng CK, Antonio Giudici, Khew SK, Koh CH, Loh MY, Tan BJ and Anthony Wong

22 April 2018

Back to Chiangmai 2018

Back to Chiangmai 2018
Butterfly Outing to Northern Thailand

A group of predominantly Zebra Blues puddling with other Lycaenids at Chiang Dao carpark

The last time I visited northern Thailand was in early October 2016. Back then, we visited the usual favourite butterfly-hunting grounds that we first discovered about 4 years ago. Compared to Singapore, these locations are 'butterfly havens' which would keep a butterfly photographer engaged for a whole day! So after a year away from northern Thailand's butterfly havens, we decided to make a trip to check out the butterfly scene again.

Look forward to a week of butterflying in Northern Thailand

After making all the necessary arrangements with our dependable and expert guide, Antonio, we got ourselves organised and looked forward to a week's worth of butterflying in Chiangmai and Chiangdao in northern Thailand. The group comprised of 'veterans' who had visited these places several times before, and we were just looking for a fun and relaxing outing this year. Some newbies who had initially wanted to join us had to pull out due to various commitments.

Our good friend and butterfly guide, Antonio Giudici also runs butterfly tours for enthusiasts from all over the world!  Highly recommended!  Refer to thaibutterflies.com for more information.

Our slightly under 3-hour flight on SilkAir was quite uneventful, and we arrived in Chiangmai International airport just before 11am in the morning, and met our old friend, Antonio. He had already spent several weeks before our trip, showing many groups of butterfly enthusiasts around good butterfly hunting grounds in Thailand. After checking in at our favourite hotel in Chiangmai and changing into our butterfly-hunting gear, we headed out to the nearby Doi Suthep and Doi Pui.

Orange Punch (Dodona egeon egeon)

Dark Judy (Abisara fylla fylla)

Relaxing and having Mrs Antonio's freshly-baked cakes for a picnic at Doi Suthep

It was already early afternoon, and the usual stops at the butterfly-rich locations didn't turn up anything new. Antonio shared with us that there was quite a bit of haze due to some bush and forest fires in the vicinity over the past week, and the air was not as clear as he would have wished. We made a couple of stops at our favourite hot spots and added a few new (or better) shots of some species. We also met Pamela Sai, an India-based butterfly photographer who travelled all around the world to shoot butterflies.

Further up on Doi Pui, it was getting overcast in the late afternoon, and the sun was fighting hard against the thick blanket of clouds. Our regular at this location, the Truncate Imperial did not show itself. However, a male Danaid Eggfly (Hypolimnas missippus) came down to play and was cooperative enough to allow us to take shots of it.

Dinner with guests Yutaka Inayoshi and Pamela Sai at our favourite Mexican joint (minus the tequila)

Dinner was at the nearby Mexican restaurant where we also met Chiangmai-based Japanese butterfly guru, Yutaka Inayoshi. He also shared with us that he was working on a book on Thai butterflies that is expected to be launched some time in the coming year or so. As usual, dinner conversation revolved around butterfly hunting adventures, new finds, unexpected rarities in Thailand.

Day 2 (Mae Kampong)

After our breakfast and a quick pit-stop at a 7-eleven outlet to buy our lunch, we headed out to the streams in the hilly outskirts of Mae Kampong. We visited the hilltop of the Chae Son National Park at an elevation of 1,517m above sea level. Butterfly activity was rather low, and Antonio shared that perhaps the season has been slightly delayed by the colder weather in the early part of the year and also the poor air quality recently.

Lesser Punch (Dodona dipoea dracon)

Cabbage White (Artogeia canidia canidia)

Staff Sergeant (Athyma selenophora bahula)

The cool fresh air lifted our spirits and there were always butterflies to chase and shoot. We checked out a few stream crossings where there were attractive puddling grounds and flowers to attract butterflies. It was a relatively cloudy day, but the butterflies were up and about.

Tailed Judy (Abisara neophron chelina)

Around late afternoon, we headed back to Chiangmai city as dark clouds loomed on the horizon. We had our fill of butterflies for the day, although we didn't encounter anything special. Dinner was at our favourite Japanese restaurant near our hotel. Considering where Chiangmai is located, and nowhere near the coast, the Japanese seafood was surprisingly fresh (and competitively priced too!).

Day 3 (Doi Inthanon)

We left slightly earlier in the morning as it was a longer drive to Doi Inthanon, Thailand's highest mountain. The roads were surprisingly clear on this day, and Antonio attributed it to the public holiday and also the forthcoming Songkran festival (Thai New Year). Many working Thais would have taken leave and headed back to their hometowns for the festivities.

Our first stop was the Princess Siribhume Royal Garden and waterfall, where we could find some unique montane species of butterflies. One such rarity was the Satyrinae, Mottled Argus (Callerebia narasingha dohertyi), which Antonio said that he had only seen a few times. Despite its rather 'boring' look, the Mottled Argus was very local in distribution and considered a rarity.

Mottled Argus (Callerebia narasingha dohertyi)

Grand Duchess (Euthalia patala taooana)

Our next destination was the Huai Sai Lueang Waterfalls. Our catch of the day was the large and showy Grand Duchess (Euthalia patala taooana), of which there were several individuals zipping around. One slightly more cooperative male came down to puddle and was friendly enough for us to even take handphone videos of it! This was a more pristine individual than the one we encountered in Apr 2015.

Exotic Lanna cuisine.  Fancy some ant eggs/larvae?

Dinner in the evening was slightly more adventurous as we sampled some exotic Lanna food, which included frog's legs and ant pupae! We were told that the large ant pupae (through which you can almost see the developing ant) were from the Weaver Ant nests that were harvested for the unhatched pupae. There were other exotic stuff which are not particularly for weak-stomachs!

Day 4 (Chiang Dao)

A panoramic view of the Nest 2 accommodation

We checked out of Dome Residences and headed out to Chiangdao after breakfast. Like on our previous trips, we had booked the Nest 2 as our accommodation. The Nest 2 is just 5 minutes drive from the now 'world-famous' Chiangdao car park. Ok, it's just famous amongst butterfly watchers and photographers, but nevertheless very popular, and a must-visit location with the fraternity of those who like butterflies.

A washout day when it rained almost the whole day at Chiang Dao

The trip up to Chiangdao took us slightly over an hour in relatively light traffic. However, it was an overcast day and the weather outlook did not look too promising. After offloading our luggage at the Nest 2, we headed to the "car park", paid our entrance fees, and set up our gear. However, the weather had other plans and the skies poured soon after. It was a very different Chiangdao carpark on this day, compared to what we experienced on our previous visits.

All ready for action! And the sun's out!

The weather did not look like it was going to cooperate, and it continued to be wet and raining the rest of the day. It was a good respite from our previous days out butterfly hunting, and for the first time, we even had time for an afternoon nap in the cool weather. The weather that evening dropped to a chilly 19degC and we didn't even have to use the aircondition!

Day 5 (Chiang Dao)

A congregation of Lycaenids (mainly Zebra Blues)

The following morning, the low clouds hung overhead and it threatened to be another washout day. However, by mid-morning, the sun peeked out and the skies cleared soon thereafter. The lethargic butterflies at the car park began to stir and very soon, the puddling butterflies, particularly the Zebra Blue (Leptotes plinius), of which there were hundreds of them, started to swarm the damp ground for nutrients.

Dark Cupid (Tongeia potanini potanini)

Common Pierrot (Castalius rosimon rosimon)

Green Dragontail (Lamproptera meges)

The diversity of species was not as good as our previous trips, but we still managed to add one or two new ones to our personal collection of butterflies shot in Thailand. It was always a challenge to look out for unique species or something special amongst the crowd of puddling Lycaenids. And there will be the odd rarity that would make its appearance from time to time.

Red Tailed Forester (Lethe sinorix sinorix)

Brown Prince (Rohana parvata burmana)

A quick drive up the winding road to a higher elevation did not turn up anything special, as we encountered the usual species that we found on previous trips - like the Brown Prince and a couple of skittish Lethe species puddling on the roadside. It was also generally low activity throughout the day at the carpark.

Day 6 (Doi Pha Hom Pok)

We moved off early in the morning and headed towards Fang, another town further north from Chiangdao, and about 90 minutes drive. Our destination was Doi Pha Hom Pok, the 2nd highest mountain in Thailand. Previous trips there yielded some interesting montane species, although this time around, we were not planning on reaching the peak where the Kaiser I-Hind flies.

Dark Jezebel (Delias berinda yadanula)

A crowd of Delias butterflies puddling

A couple of stops along the key puddling grounds did not turn up anything special, although this time around, there were lots of the Dark Jezebel (Delias berinda yadanula) in season and were fluttering all over the place. Other rarer Delias were also around, but challenging to locate amongst the crowd of the commoner species.

Stately Nawab (Polyura dolon grandis)

Antonio supervising the photographers

Interestingly, there was a bunch of the Stately Nawab that came down to puddle for about an hour, and we counted a total of 8 individuals in the vicinity, and several of them were tame enough for handphone videos of them puddling. Diversity was still low, and Antonio wondered if it would be better in the later part of the month. Although it sounded like we were complaining about the lack of butterflies, it is only because our earlier trips had "spoiled" us with much greater numbers!

Day 7

A giant amongst the dwarves, Tawny Rajah (Charaxes bernadus) amongst other Lycaenids

This was our last shooting day in Chiangdao and we spent half a day at the car park. It was a hot sunny day, and the temperature soared to about 35degC by midday. More species were up and about today, and interestingly many individuals were very pristine, probably having just eclosed that morning. The crowds of Zebra Blues continued to dominate the puddling grounds.

Pieridae to the left! Papilionidae to the right! Taxonomically organised puddling!

An aberrant Zebra Blue

There were more Papilionids turning up at the puddling grounds as the day progressed but the hot humid conditions made it very exhausting to shoot them. All too soon, we had to call it a day and we piled up our luggage and headed back to Chiangmai city. Despite the relatively lower butterfly activity on this trip, we were more selective at what we wanted to shoot, and felt more relaxed and enjoyed ourselves.

The Vagrant (Vagrans sinha sinha) was common at Chiangdao this season

The following morning, we bade farewell to our good friend Antonio, as he dropped us off at the Chiangmai International Airport. Until the next time, adios Chiangmai, Antonio and all the butterflies of northern Thailand. I'm quite sure that we'll be back again in the near future!

Cheers! and to the next Chiangmai outing!

Text by Khew SK : Photos by Huang CJ, Khew SK and Loke PF.