Trip to Singapore: March - April 2006

Results and reflection on this trip

Personally, I feel that this trip was in fact slightly more productive than the previous one last year. I returned with less specimens this year, but this was only because I did not bother catching certain species of which I had taken many of the previous year. I still managed to collect a considerable 43 specimens.

From what I have observed during the recent 2 trips, activity in the tropics is slightly seasonal, but in a different way from sub-tropical or temperate regions. Certain species appear to be present throughout the year, however. These include the large carpenter bees, Xylocopa confusa and Xylocopa latipes, as well as the banded paper wasp, Polistes sagittarius. Vespa affinis has been the most consistently common species both in the past and of recent times. On this trip, I even found many males and queens! But workers were also present, although not in such great numbers as before. Perhaps it was because many of their favourite food plants, such as coconut and certain flowering shrubs, were not in season during this period. The coconut and other palm trees started blooming towards the end of my stay, and that was when I saw an increase in numbers of this species.

I successfully obtained Vespa tropica specimens this time. Comparing specimens of Vespa affinis, Vespa tropica and Polistes sagittarius from Singapore with those in Hong Kong, I can say that they show the same differences in appearance: in Southeast Asian specimens of these three species, the head and thorax are completely black and lacking in any brown or red markings, while those in Hong Kong usually show conspicuous red heads and pronotum (the frontal side part of the thorax). Also, the specimens I have taken in Singapore all seem to be conspicuously larger than their Southern China counterparts. The Vespa tropica are an exception, although this is only because the two specimens I managed to obtain were exceptionally small. Some other individuals I saw were impressively large.

One of the most exciting discoveries must have been the huge aerial nest of Vespa tropica. This species is usually ground-dwelling and builds its nests underground or in crevices such as hollow tree stumps. Therefore the location of the nest, originally probably 14 feet above ground, coupled with its enormous size, was totally unexpected. According to what I have heard, Vespa tropica may indeed build above ground more frequently than expected in equatorial regions. Besides this, the other hornet’s nest (probably Vespa analis) and the several Stenogastrine nests were also great finds. It was a pity I found the Stenogastrine nests so late and had no time to observe them further, since there is still much to be learnt about these little-known, secretive wasps.

For the first time, I caught the small, red and yellow Polistes I saw in photos on various local photography and nature forums. By the size, the dark spot (stigma) on the wings and the record for Singapore, I can now confirm this is indeed Polistes stigma. Interestingly enough, as previously mentioned, it appears that there are two separate colour forms of Polistes stigma in Singapore. The other colour form, which I saw but did not manage to catch or photograph, is mainly black, with just slight red markings on the legs, and some yellow markings on the abdomen. Strangely, the two colour forms seem to have a distinct separate range. Based on my personal sightings and enquiries to different photographers who have seen them, the black form seems to be prevalent inland or among disturbed vegetation and secondary forest areas. The red and yellow form, however, appears to be coastal and found mainly near mangroves. Such geographical/environmental separation is of course not unusual, but for the fact that Singapore is already so small!

I also saw another colour form of Polistes sagittarius, which showed the same yellow band but had all usual black colouration replaced with light brown! I did not have enough time to search around the area and search for some way of finding out whether this was just an aberrantly coloured individual (possible), a newly hatched worker which hadn’t hardened and dried up yet (unlikely; she was actively hunting) or a separate population or colour form (quite possible). I was also unable to find the nest of Polistes sagittarius, although I knew for sure that there were several colonies near my place.

I now know for sure that another species of Polistes exists in Singapore, in an urban condominium no less! The number and development stage of cells on the nest indicated that this nest was not a very young one. The cells were far too large for Polistes stigma, and considerably smaller than Polistes sagittarius. What could it be? Polistes olivaceus? The checklist by Carpenter* lists this species as being present in Singapore, which is completely possible, given that this species is widespread across much of Asia and has even been introduced elsewhere (Reunion Island and Hawaii, among others) due to its adaptability and frequent close proximity to populated areas. However, I have never seen this easily recognizable medium-sized bright yellow wasp in Singapore. Also, the cells, while being too small for the fairly large Polistes sagittarius, look a little bigger than cells of Polistes olivaceus which I often see in Hong Kong. I shall have to search harder in future. A friend mentioned he saw a Polistes species (he is sure it is a Polistes because I pointed out Polistes sagittarius and he recalls it being the same shape and having the same manner of flight), even larger and uniform brown in colour. Polistes gigas? Almost certainly not. This huge species is found only in the South China and Southern Indian regions. Anyway, the size he claimed it was, while considerable, falls short of Polistes gigas. Perhaps Polistes tenebricosus; this is a large species, commonly fully brown in colour, found in Indonesia, Malaysia and Taiwan.

I found Parapolybia in Singapore when I was least expecting to. Having all three species of East Asian Parapolybia in Hong Kong, I am very familiar with the foraging and nesting habits of these wasps, but though I searched hard throughout the previous trip, I was unable to find signs that these wasps do occur locally. This time round, my attention had been diverted to other things, and I found one just like that! Still, I wonder how come they are so rare and secretive here. Parapolybia form fairly large colonies, averaging 200 or 300, far larger than most Polistes colonies. Furthermore, I would have thought that these adaptable scavenging wasps would be everywhere, feeding on carrion and even attempting to take human food (there are lots of outdoor dining venues in Singapore). I wonder if the nests are similar to those in Hong Kong, how large the colony can get and how long it can survive. Although these wasps are by no means specialized in their choice of nesting sites (a wide variety of shrubs, small trees and even building roofs), Parapolybia varia in Hong Kong are especially fond of nesting in ornamental Ixora bushes in urban parks. There are many of these bushes in Singapore, so I shall search them in future. I also have much to learn about the various Ropalidia species. I have personally seen three, and recently saw a fourth species in a photo taken by someone else. This resembles the black species with a red gastral petiole (“waist”), but lacks this red colouration and has a narrow yellow band on the abdomen instead. It seems that there is enough to keep me occupied for many trips to come, and this suits me fine! Singapore is not a very exciting place to be for more than a few days, and I am so glad that I am able to spend much time on wasps during my holidays back there!

A 1972 paper titled “Hornets of Singapore: Their identification, biology and control” by K.L. Chan states that “there are only three species of hornets in Singapore: Vespa affinis, Vespa analis and Vespa tropica.” An online list based on a checklist by Kojima and Carpenter (some of the foremost experts in this field), however, states that a species known as Vespa multimaculata is also known from Singapore, and Archer (another foremost expert) also mentions this. I am still unable to explain what the two mysterious hornets I saw (one on my previous trip, one on my recent trip) are! The giant black hornet with a thick-set yellow head I saw in June 2005 on Sentosa, and the plain brown one at Alexandra Hospital this April; both do not fit the description of Vespa multimaculata, which is supposedly a small hornet with abundant yellow markings. Therefore, personal sightings of these two strange hornets, together with the few encounters I have had with the elusive Vespa velutina, and the other known local hornets Vespa analis, Vespa affinis and Vespa tropica bring the total number of Vespa species to 6! This is exciting and I hope to have a chance to look further into this in future. I hope to find a way to verify the local existence of Vespa multimaculata too; this would bring the number to 7.

A rough illustration of the brown hornet I saw. The drawings below copyright of Damien Teo. I simply coloured them to match what I saw.

This illustration and the photo below depict the giant hornet I saw on my 2005 trip. The photo was simply a photo of Vespa soror, edited to make the rest of the body look black. This was exactly what the hornet I saw looked like!

As I also wonder regarding Parapolybia, where do Vespa velutina nest in Singapore, and why are they so elusive and rare, considering that this species is highly adaptable and has extremely large colonies? Perhaps they aren't doing well here. Although this species is found in Malaysia and Indonesia, it is mainly a mountain species in tropical countries, so it is surprising. Starr (another knowledgeable expert) found Vespa velutina absent in lowland areas where both Vespa affinis and Vespa analis occur, possibly as a result of competition.

Unfortunately, much of Singapore’s original forest has been cleared off. Singapore does have a small patch of primary rainforest (original forest which has suffered relatively little disturbance), but many other natural habitats such as other patches of forest, seashore or mangrove have been cleared to make way for new developments. Many of the local reservoirs, which I have found to be fairly rich in insect life, are also going to be redeveloped as recreation sites in the near future. Furthermore, the planned Integrated Resorts (the subject of much debate recently due to concerns about a casino in Singapore) are going to be built on the site of the Asian Village in Sentosa and on Marina South, two areas with surprisingly diverse insect fauna and with great potential. This is quite unfortunate. It is certainly possible that the rarer species of hornets (and many other insects) dwell in specialized habitats. This is seen in a number of species elsewhere; for instance, Vespa vivax (Nepal, India, parts of China), Vespa wilemani (Taiwan) and Vespa mocsaryana (Malaysia) are said to be restricted to mountain forests. Even in Singapore, some species appear fairly specialized; for instance, the red colour form of Polistes stigma is almost always found near the sea or mangrove areas. I hope I will be able to catch and establish the identities of the two mysterious hornets, as well as Vespa velutina, Vespa analis and possibly Vespa multimaculata, before places which may well be the last remaining habitats of these species get destroyed.

Speaking of Vespa analis, this species was supposedly common in the past but is now rare. Or maybe I was simply searching the wrong places or at the wrong time? But I do think certain factors may have influence in this. Vespa analis usually nests in trees, but usually at a lower position than Vespa affinis. They are reportedly very fond of rambutan and mango trees and other similar types. I am thus wondering if a species of ant, Oecophylla smaragdina, could be at least partly responsible for the decline of Vespa analis. Mango trees are common in urban areas, and for some reason, every single such tree (and many other trees and shrubs, for that matter), are populated by these ants! It is rare nowadays to find a tree not inhabited by these ants, which are large and red in colour; they are extremely defensive, and although they cannot sting, they bite and spray acid into the wound, causing great discomfort. Their nests, made of leaves held together with silk produced by the larvae, can reach large sizes and sometimes several nests are even linked across several trees and the ants travel freely between them! Any insect living in such trees usually gets dismembered and eaten, and the ants often monopolise the tree and the surrounding area (they caused lots of damage to my trapping plans by using my pan traps as hunting platforms). They nest at just the exact same height and area as Vespa analis, so it is not surprising that they have out-competed these hornets for nesting sites. Ants remain one of the few creatures capable of wiping out whole colonies of social wasps. Vespa affinis is possibly not affected so adversely because it nests much higher up on average and may not be subject to the assault of these ants. This is, of course, simply an educated guess, but it is indeed a distinct possibility.

The Apis florea nest was another great find. I consider myself fortunate to have been able to take a photo of the structure when the nest was almost fully mature, with queen cells at the bottom. The division of the nest was amazing. Unfortunately a honeybee nest is made of wax, and the weight of the honey inside would have caused the comb to break if I lifted it off the ground (I could feel it already starting to collapse when I pulled the nest off the branch). Also, it was wet, not light and dry like a wasp nest, so there was no way I could keep it. A pity the honey inside was also contaminated by insecticide!

Singapore remains rather rich in solitary wasp and bee species, although I didn’t see so many bees this time. Again I believe the season was not right, because many flowers had not started blooming. I was fortunate enough to be able to photograph one of the beautiful beach-dwelling Sphecid wasps in the act of carrying a fly, as well as making some new observations on their behaviour. It is good to know that they are still thriving as before. I have yet to find out the prey species caught by the very large black Sphex species in the same area, however. I hope to be able to document the behaviour of different solitary wasps in future, but their habits are so diverse and I think it is going to be difficult to even start counting the number of species present locally.

I could go on and on about this trip and what I found, but I think I’ve said enough. In short, this trip was a great success and immensely enjoyable. I may be planning another trip later in this year. You may be wondering, why not try somewhere else? Singapore is such a small and urban place. I would certainly love to visit natural habitats in other places such as Malaysia or even Central and South America, but due to my schedule and other factors, it is not practical at the moment. Furthermore, I personally like to thoroughly investigate a small region, as I have been doing in Hong Kong the past few years, and even then I still occasionally find something new. The variety of species in Singapore does seem more than that in Hong Kong, and that will keep me busy for years to come. The behaviour and colony cycles of social wasps are also a lot more unpredictable and more of a challenge to investigate. I intend to hunt down the mystery hornets mentioned above and confirm their existence before they vanish locally, which may well happen if more habitats are destroyed. This said, I may be planning a trip to Taiwan in the near future too; I would like to personally observe the greatly feared hornets Vespa mandarinia and Vespa basalis in the wild.

A couple of other photos taken on this trip

A view of my estate just before a sudden thunderstorm. Note how half of the area is still bright and sunny. The cloud crept over in what seemed like mere seconds, and thunder struck barely 10 minute later.

Another storm. A rather productive and exciting hunt was cut short by this.

Scenery at Jurong Lake, near the Chinese Garden. Although I did not manage to photograph or collect anything, the area looked promising. I saw some of the largest dragonflies I have ever seen here.