Three months with a colony of Vespa soror

This chapter describes time spent watching a colony of Vespa soror. Note that I had formerly not known the existance of this species in Hong Kong, instead assuming they were Vespa ducalis! I have since revised this chapter, and added photos which I had completely forgotten about! From further experience with this species in the recent few years, it is in fact a highly territorial species which often attacks hikers! I was lucky to get away unharmed by this colony, but through this experience I once again prove that even the more defensive species of hornets will usually content themselves with driving an intruder away from the vicinity of the nest and will not resort to stinging unless truly necessary. Finally, I recall that during all the time I spent with this nest, although I was very close, I was not in the flight path of the wasps at all, and this is an important factor which determines whether a colony sees one as a threat or not.

It was a typically hot day in early September when I decided to take a new route. I was alone near a nature trail which I frequently visit. Having visited quite frequently over the past few weeks, combing almost every tree and shrub in the process, I was unable to locate any new nests; I had already found several nests of the lesser paper wasps (Parapolybia nodosa, Parapolybia varia and Parapolybia indica), and two nests of the hornet Vespa velutina. Therefore, I decided to venture into a trail which I had never entered before.

This trail led to a small rocky dirt path, unlike the neatly maintained concrete of the main visitor’s section down below. There had been talk of robbers in Hong Kong’s country parks recently, but I decided that due to its proximity to human dwellings and the fact that this trail seemed short (I was right; it only takes 25 minutes to complete!), I picked up a suitable-sized pole of fallen bamboo, gave it a few test swings and climbed a long flight of stairs to reach the main part of the trail. Halfway up the stairs, I spotted another nest of Vespa velutina, in a much lower position than usual. I decided to return to photograph it on my way down.

Venturing a little further, I saw a worker of the hornet Vespa soror, flying towards a small slope on the “wall” at the side of the path. Most country park trails in Hong Kong do not proceed directly into the forest, but are instead easily accessible paths which have a wall of sandy or stony cliff on one side, while the other side trails downwards and is blocked by undergrowth. I rushed forward to watch what the hornet was doing, and possibly to photograph her. Vespa soror is a very large hornet; it reaches sizes similar to the Asian giant hornet (Vespa mandarinia). Imagine my surprise when she disappeared into a crevice, and immediately, another two emerged and flew away. I had stumbled upon a nest site!

Although it cannot be considered very rare, Vespa soror is one of the more uncommon species in Hong Kong, and apparently quite restricted in range. It does not seem to take pollution well and is only found regularly in country parks and rural areas with cleaner air, and also seems to require real forested habitat for colonies to thrive. I have seen very few colonies of this species, but this was a typical nest site. The soil surface of the cliff had fallen over an old tree stump to form a little platform or “table”, roughly 2.5 feet off the ground. The founding queen had apparently dug into the innermost corner and started her nest inside. In Hong Kong, nests of both this species and other ground hornets such as Vespa tropica (greater banded hornet) and Vespa ducalis are almost always built out of view, hidden in an underground crevice.

I stood and watched, fascinated, as a procession of workers started to appear at the entrance, marching out in a straight line, each carrying something in its mandibles. It quickly became apparent that they were excavating the clayey soil and enlarging the nest cavity, to allow for expansion of the nest. It was a truly fascinating process to watch. They would carry the balled-up soil and drop it off the edge of the platform, where it fell into a neat pile on the ground. They would then walk back into the entrance, which was nearly two feet from the edge where they dumped the soil, while others emerged with more loads to dump.

I approached cautiously. I did not think they would be overly defensive of the group, but I moved closer step by step, just to be on the safe side. As expected, the 3.5cm long gentle giants did not even react to my presence, now merely a foot from the ledge. I bent slowly and picked up a handful of the soil pellets. To my surprise, they were neat, spherical pellets which had hardened and felt like clay. The hornets had apparently effectively compacted them well, and they dried fast. I put one on a smooth rock and attempted to smash it with my knuckles – it took five solid blows to do so! I would later find out that even after rain, the pellets remained intact, in a neat pile at the foot of the nest site.

I could have stayed all day to watch them, but I had other things to do. I made a mental note of the location and left. I attempted to photograph them, but did not get good results due to poor light and the use of a long, heavy lens. Since I had the following two days off, I would go back and spend some time observing them.

I returned early in the morning on the following day immediately after breakfast. I brought a small foldable chair and my tripod. Once again, I cautiously approached, and finally placed the chair a mere foot in front of the nest site. I then set up the tripod, mounted the camera on it and got the focus correct, so I did not need to peer through the viewfinder all the time. I could simply reach out and depress the shutter release whenever I observed something interesting.

It was a pleasure to watch the industrious hornets at work. There were 9 or 10 workers involved in the excavation, while several others alternately returned and left, occasionally returning with something held between their mandibles and legs. I could distinguish two different types; the brown, flattened material was probably wood fragments which were to be used to construct nest material. Some workers also returned with prey; I could not tell what insects they were, but they carried a variety of insect parts. I saw workers returning with green objects, which could have been caterpillars or grasshoppers; I have personally seen this species catch both, in addition to large butterflies, dragonflies and even spiders.

I took many photos, but was not satisfied with them overall. I decided to do something which was actually quite risky. I would not have done it with any of the other local hornets, but I felt attempting this would be worth a try. I fixed another lens to my camera; this lens enabled me to get a good overall impression of the excavation. The snag was that I had to get close to some of the workers. I moved in steadily and at a snail’s pace, and got one good shot. The lens had been a mere nine inches from some of the workers, and yet all they did was to turn and look in an almost curious manner before continuing their work! I was amazed; I never expected them to be this approachable.

The next day, I returned to the nest and did something even more risky. I brought a grasshopper with me, and sat in front of the nest as usual. When one of the workers dropped her load of soil, I held the grasshopper out headfirst, touching it against her antennae. She pounced on it and proceeded to bite fiercely; she carried it not towards the nest entrance, but to the far end of the ledge, where she continued biting and chewing till the wings, legs and shell had dropped off and only a ball of flesh was left. She then walked all the way back into the nest. What an experience! I was shaking slightly from going so close to a worker in the vicinity of the nest, but it was worth it. I did not attempt to take photos, as I felt that any slight vibration caused could result in a defensive attack by the colony.

I must, at this point, again mention that I took such liberties only because I assumed them to be Vespa ducalis, which is known for its docile nature and reluctance to attack humans. Had I known they were another species, especially one so closely associated with the feared Vespa mandarinia, I would never have gone so close! However, ignorance is bliss, and I have since learned that Vespa soror is not nearly as quick to attack and sting as I have been told by local hikers.

A couple of days later, I took some free time in the afternoon to visit the nest site again. From a distance, I could already see that there was somewhat more activity than usual, and the wasps were flying in different directions, not using their usual flight path. I started to approach, but when I came within five feet of the nest, one of the workers flew straight for me. I didn't have time to think, I knew that the nest had been disturbed and the hornets were ready to attack anything in the vicinity. These hornets also have some of the most painful stings in the insect world. I started to back off, but the hornet gave chase and slammed right into my head. I stood still and braced myself for the sharp burst of pain that comes with a sting. But that never happened. I was aware of the hornet stuck in my hair, and I backed off a few more steps and used a branch to pull her off. To my surprise, she was unable to fly any more, and was helplessly struggling on the floor, jabbing her 5mm long sting into the air. Near the nest, more of the frantically circling workers were crashing around on the path. Some were still flying, and I realized that they were not going about their business in their usual purposeful manner; they were circling agitatedly. This was clearly no small disturbance to the colony, and despite the risk of getting stung, I had to find out the reason. I cut off the main path into the undergrowth at the side to avoid passing the flight path, and, from a safe distance, surveyed the nest entrance. The destruction around the area was completely unexpected.

Someone had attempted to exterminate the nest, using insecticide. I couldn't tell what type of insecticide, but the pile of earth that had formed outside the nest was soaked with an acrid-smelling liquid. Even as I watched, the circling workers started getting weaker and falling to the ground, thrashing around helplessly. Others returned to the nest site with food only to fly around in confusion, no doubt not being able to recognize the scent of the nest area since it was now drenched with the deadly chemical. And the hornets were not the only ones affected. Several dragonflies were knocked down by the insecticide and were beginning to die. A couple of large butterflies were already dead. A bush cricket lay on its sides, kicking out with its large back legs. A usually swift and shade-loving litter cockroach crawled out into the open. It later died there in the very same spot.

It was quite sad to see these magnificent, industrious insects meet such a painful end. I was also rather annoyed at this senseless act. It could have been done by government staff, but it was quite a shabby job, obviously done by someone with minimal knowledge of how to exterminate a nest. I found it ridiculous for someone to enter a country park, a protected area, and flood a patch of nearly nine square feet with insecticide. A stone had been thrown to cover the entrance; this, however, was obviously done from a distance and anyway a stone is never suitable to block a nest entrance. A closer look revealed that the insecticide had been sprayed mainly on the mound of excavated soil, and not into the nest entrance. Still, I wondered how much insecticide had entered the nest. I later collected 13 of the dying hornets to preserve as specimens.

I returned three days later, intending to dig out the cavity and get a good look at the nest; I assumed it would probably be safe to do. I was fortunate I didn’t even get started. The minute I reached the area, I saw a worker leave the nest. She flew off in the usual steady, calm way, with no sign of aggression or being affected by the chemical. Dead wasps littered the floor; I counted another 10 in addition to the 13 I collected the day before. Just then, another worker returned. I was surprised that there were surviving individuals, but perhaps the pesticide had not penetrated into the nest itself. The nature trail was only 15 minutes by bus from my place, so I dashed downwards at top speed, jumped onto a bus and went home. Grabbing a net and an insect marking kit, I returned to the nest site and netted the workers in flight. I marked two of them, one with a blue dot, one with a yellow dot, then released them several feet away from the nest. I only had three colours in the kit, but it was sufficient, because it seemed that there were only two survivors; I waited for more than an hour but did not see any other individuals. I was also thankful that they reorientated and went about their business upon being released, instead of charging at me! This was my first attempt at catching and releasing near the nest.

I continued to visit the site daily. Since the location was so near to my place, I visited the nest site every day after breakfast. I make it a point to do an hour of vigorous exercise every morning, to keep fit and for health reasons. The area surrounding the nest site was quiet and tranquil, and since I was missing my daily exercise by visiting the nest site, I decided to exercise there instead! In fact, my usual routine seemed more challenging on the rocky, uneven terrain, but the feeling of satisfaction was far greater than usual. I was also able to keep watch on the nest in this way. For two weeks, the two workers struggled to provide for the colony. Vespa soror is usually slow and steady in flight, and I was able to distinguish both of the workers I had marked. I noticed that worker 1, with the blue dot, was involved more in hunting, while worker 2, with the yellow dot, constantly brought new material for construction of the nest. I never saw them stop for a break! It was during this period that I saw worker 1 return with a large, heavy-bodied orb-weaving spider (Nephila sp.), which was no smaller than she was. How she managed to capture such a formidable creature, I truly do not know. I was glad to know that the queen and her offspring were probably still alive; that was probably the driving force behind the tireless work of these two workers.

The following week, I was pleasantly surprised to find that several new workers had hatched! They had already started to perform tasks around the nest entrance and even take short flights. Newly emerged adult wasps are usually nest bound for the first couple of weeks, working on nest repair, feeding of larvae and other such tasks. It seemed that the new workers of this colony had been forced to take on other roles due to lack of “manpower”! Or could it have been that these workers had already emerged a couple of weeks back, but were still not ready to start foraging?

It was a pleasure to see the colony slowly regain its old numbers. From the two surviving workers which strived so hard to preserve the colony, the population grew back to a great number. The excavation also resumed, and the wasps seemed to be gathering building material at a frenetic pace; I even saw one chew dead leaves up to be used to expand the nest! Apparently they knew it was time to allow the population to grow even further. I continued my routine of exercising near the nest, while keeping an eye on them and looking out for anything unusual. I never ceased to wonder at the fact that my fast-paced and vigorous movements, merely several feet from the nest, did not bother them at all. They were the same old gentle giants.

Above: A guard which was always at the entrance, inspecting all returning workers.
Below: One of the workers chewing dead leaves outside the nest to be used as nesting material.

Sadly, I did not see the original two workers with the coloured dots again after a couple of weeks. They could have been killed by predators or people, got lost, or perhaps simply expired of old age. My admiration for social insects was stronger than ever; without those two determined workers, the colony would surely have perished.

I found the wasps far more reluctant to sting in defense than I would have thought. There was a large male changeable lizard (Calotes versicolor) which frequently lurked near the nest site, trying (often successfully) to secure a satisfying meal. This lizard was no fool; he waited till the line of workers involved in the excavation thinned out, then rushed out to grab a single unsuspecting hornet who had just dropped her load. He then sped off to a branch above to feast on his catch!

Above and below: Photos of this lizard. I did not even realise I had captured a couple of shots (though not very good ones) of this lizard near the nest site until I reviewed some of my old batches of photos! This was his usual hunting posture; unfortunately I never managed to get him in the act of capturing a hornet.

One morning, his luck ran out. While attempting to catch a worker at the edge of the platform, three others suddenly jumped on him. They attacked him ferociously with their mandibles, biting him repeatedly on his legs and body, but surprisingly, I did not see them use their stings at any time. The lizard easily shook the hornets off and darted off down the forest path.

Summer turned to autumn, although the weather throughout autumn and winter was unusually warm this year. I eagerly anticipated the emergence of males and new queens. In fact, I suspected that if I continued to visit the nest regularly, I might one day witness males and new queens mating! Males of Vespa soror can be seen locally from November to January every year; this species has a long life cycle. November was just around the corner, and I fervently hoped I could observe something new this year. Sadly, this was not to be so.

I went up the trail as usual one afternoon, and saw a cloud of the wasps hovering around the nest site. I was excited; this could be mating in progress. On the other hand, memories of the previous incident were still vivid in my mind, and I did not want to risk being attacked again. I cut through the undergrowth as before, and emerged on the other side.

It was definitely nothing to do with mating. The wasps were almost as agitated as before, and I could see why; the soil surface of the cliff had caved in, and the nest entrance could not be seen! I couldn’t tell whether it was due to natural causes or if someone had dug at the cliff surface to cause the soil to cover the entrance. It was quite strange, given that the colony had survived throughout periods of heavy summer rainfall. Furthermore, it was now quite dry, and there had been no rain. I decided to return a couple of days later, to give them time to settle down.

Upon my return two days later, I found that the wasps had made a new entrance hole, this time located at the foot of the stump, at ground level. They seemed to be calm now, going about their usual activity, so I sat in front of the nest entrance and poised my camera, hoping to get some photos of the new entrance. Even before my finger touched the shutter release button, a worker crashed hard against the side of my head. I assumed that one of the workers leaving the nest had simply accidentally collided with me. But something was wrong; she did not reorientate and leave or return to the nest as would have been normal, but aligned herself at head level, and in a split second, flew straight at me, this time crashing hard into the center of my forehead! I realized I was under attack, and slowly backed off a few steps, but the wasps had already been agitated. Another two or three workers emerged from the nest entrance, and in the same determined, tenacious manner, made several darts at me. The way in which this happened was surprisingly “choreographed”; they took turns to attack, hovering menacingly just several feet from my head in between. Such an unexpected attack from such large wasps was an experience I had never been through, nor had I ever imagined. The substantial weight of such a large wasp crashing hard into one’s head has a frightening effect. I was rooted to the spot, partly from shock, and partly from fascination! Finally, I found my legs, and backed off steadily. At around 5 feet from the nest, the frenzied attacking stopped as suddenly as it had begun; one worker made a final dart for my head, but did not make contact. Then normal activity suddenly resumed; it was as if nothing had happened.

I sat on the forest floor, trying to catch my breath and marveling at my close shave. It was a wonder that I had escaped many painful stings and even possible serious envenomation, but what amazed me most was that they did not use their stings once, even though what happened was distinctly a defensive attack!

At any rate, the wasps were visibly upset by all the recent happenings. I now had to keep a safe distance of at least 5 feet, where I was still able to continue observing them. On several occasions, I went up with a friend, an enthusiastic photographer who wanted to get some shots of the nest. With his long lens, he managed to photograph some workers carrying green objects. When the photos were enlarged, a closer look revealed that they were carrying parts of a mantis! In fact, we observed this quite a number of times; this indicates that Vespa soror frequently attacks and kills mantids! These hornets are truly formidable predators to be able to achieve this.

We were photographing near the nest one afternoon, and decided to move closer to get better shots. My friend’s monstrous 300mm f2.8 lens, which was huge and black, must have alarmed the hornets; we had barely started to shoot when a large worker crashed into my friend! More came out of the entrance; in an instant, all activity ceased as the workers went into an alarmed state. Some of them came at me, and I received several hard knocks from them. We beat a hasty retreat. Again, we did not receive a single sting. My friend swiped at them with his hand, as anyone would have done out of reflex; not surprisingly, this angered them further, but yet he was not stung!

I shot this photo just seconds before running. An obviously displeased hornet shoots vertically out of the nest entrance; barely a second after this photo was taken, she hit my friend right in the forehead!

Later in the week, I went up and found the wasps circling agitatedly yet again. When I approached cautiously as before, the new entrance hole had caved in yet again, and this time, it wasn’t just the soil which had covered the entrance; cement had been poured over it! This was certainly done by people. The wasps couldn’t get back into the nest, and appeared to be emerging from another spot, even higher than the old one. I did not dare to risk photographing them in this state, so I left, and returned the next day.

A horrific reminder of the first attempt to exterminate them greeted me. The acrid smell of pesticide, dead and dying workers, some still circling aggressively. On top of that, much of the platform was now covered with more cement. In spite of this destruction, the wasps had opened a new entrance, hidden away in another corner of the cliff surface. But the damage had been done. The remaining workers struggled valiantly for another two weeks to keep the colony going, but eventually, the nest site was lifeless. Apparently, a longer-lasting residual pesticide had been used, exposing each wasp to it upon leaving or returning. The queen and any remaining offspring had probably starved to death or been exposed to the chemical brought in by the returning workers. Sadly, this marked the end of the colony I had become most attached to. And I never got to see any matings.

On hindsight, I could not blame the ones responsible for this. The nature trail, although quiet, was still sometimes used by joggers and hikers, especially during the weekends. And though the flight path led away from the trail and thus anyone passing would not be directly in the flight path, these giant hornets would have seemed terrifying to anyone who caught sight of them, especially during the excavation process, where numbers of them marched in and out. However, it was quite sad that this particular spot, to this day, is still quite dead, as compared to the rest of the trail. I do not see any more spiders, flies, dragonflies or crickets; these used to be plentiful, but the pesticide seems to be keeping them away, several weeks after it all ended. Also, I felt that if done by government staff on official orders, the area should have been cordoned off till the extermination was completed, and that if outsiders were responsible, they should never have taken things into their own hands. The previously gentle hornets became a serious menace to anyone walking past after they were agitated time and again by attempts to kill them.

As mentioned above, I was most fascinated with their defensive tactics. Although clearly in an agitated state, I noticed that they did not appear to use their stings. From personal experience, the sting from Vespa soror causes considerable pain; it is akin to being pricked by a thick needle which was first heated over a flame! Therefore there is no reason why their stings could not serve as an effective defense. I guess if I had stayed longer and continued to pose a threat, I would have been stung. I can only say that contrary to popular belief, Vespa soror and many other hornets are content to drive an attacker away and will usually give warning well before stinging in defense. I believe this would be an interesting subject to research into, although I have no desire to attempt such without adequate preparations!