By Sharon S. Lim

Isn’t it great to have nature right at your doorstep? Some of you have olive-backed bird nesting outside your study room, colourful butterflies hovering around and laying eggs on your potted plants in your garden, spider spinning giant web in a corner of your ceiling, chameleon playing peek-a-boo with you on the tree and many more.


Well, I had a strange encounter on 15 March 2010.  As usual, I watered my plants before I left for work. To my surprise, a peculiar looking muddy dish, carefully shaped on the stem of my bamboo plant, greeted me that morning.  I did not examine further and left it alone. When I returned in the evening, I was a little shock and happy to see a little pot.


Out of curiosity, I took an image of it and posted it on NPSS website in the hope that someone would be able to identify. Within 5 seconds, Lee Phek Thong kindly shared that it could be a pot built by a Potter Wasp.  So what exactly is a Potter Wasp? How does it look like?  How did it build the pot?  Where is it? What is the green fat wiggly caterpillar doing in the pot? How did it get into the pot?  All these unanswered questions were truly worth investigating.
Without much hesitation, I searched the web for some answers.  Bingo!  Potter Wasps get its common name for their vase-like pot from mud. They are in the same family as Vespidae, and belong to a distinct subfamily known as Eumeninae.  I was fascinated and thought it would be great to meet the Potter Wasp that was responsible for the pot.  My wish came true the next day and I saw a black and brown insect, about 2” in length. It was long and thin with an extended petiole (“waist”), linking the thorax and abdomen.  In fact, I saw the same insect a few days ago around the site and I did not know it was a Potter Wasp.
By this time, the tiny opening of the first pot, which looked like a fluted neck, was already sealed with mud. The Potter Wasp was hovering around its pot as if adding more mud on top of the existing pot. I quickly placed my camera near it and it flew to my tripod as if to check out what it was doing near its pot. It then flew away! When I returned in the evening, another pot was built on top of the first.  It looked exactly like the first pot and it was about 1″ wide, 0.5″ tall and 0.5″ deep.

By 19 March, there were 5 of them.  Hazel Han wished that the pots were transparent so we could all see the development of the larvae.  It rained heavily the same evening.  I was at work then but thinking of the pots because my bamboo plants were placed in an open balcony.  I was afraid the pots would be washed away since they were made of mud.









Well, rain or shine, they withstood it all.

I also noticed that when the Potter Wasp is at rest, the wings are held at an angle instead of folded over their backs at a very narrow or overlapping angle. Adult Potter Wasps feed on flower nectar and collect small caterpillars to feed their young. To build their pots, it will visit a rather wet or Normal 0 false false false MicrosoftInternetExplorer4 moist patch of sandy soil or mud, moulds some mud into a ball and flies back to her chosen site, and moulds the mud into place before taking off to collect more. The mud dries very quickly, so layer after layer is quickly set in place. However, the Potter Wasp usually makes a great many mud-collecting trips just to set up one pot. Once the pot is almost done, it will hunt for its prey. Potter Wasps are important in the natural control of caterpillars because they usually use the pest species of caterpillars. It will grip the caterpillar with its robust mandibles, pin it down and sting it.  By doing this, it paralyzes the caterpillar without killing it. It will then fly back to its pot, dragging the caterpillar along in her mandibles.  The paralyzed caterpillar is placed into the pot. Some species put several small caterpillars into a single pot, while others use just one larger one.  The Potter Wasp then deposits a single egg in the pot through the entrance before it seals it up with another layer of mud. The larva consumes from 1 to 12 caterpillars as it grows.

When you see a Potter Wasp, do not be alarmed.  Potter Wasps, especially the solitary ones, are very hard to aggravate to the point to where they attack, and when they do sting you, it is not painful, as its venom is meant for paralyzing small caterpillars or spiders, not harming large animals like humans, or even a guinea pig.


So what next after 5 sealed pots? By this time, more questions came to my mind.  When will the larva emerge? How will it emerge from the pot?  Allan Lee guessed that the Potter Wasp probably covered the opening with a thin layer of mud so that the young adult can break free easily.  It was not the case as you can see in this image. I was pleasantly surprised to discover a new pot the next day and it was right smack on top of the first pot!  It did not stop at 6 and continue to 9 by 31 March resulting in a multi-unit residence.  It got so heavy that it tilted downwards and I had to tie it to a thicker stem of my bamboo plant.  At times, you can see through the tiny opening that it is empty.   I figured it does not necessary mean that the Potter Wasp puts its prey before it completes the pot.  In this case, the Potter Wasp has to search for small caterpillars to thrust them through the opening, which is only about 0.25”.
Around 10 April, there was a little hole at the back of the first pot.  The next day, I found another on top of it.  The gap between each opening was about 0.39”.  As you can see, the opening is different from the corrugated ones shown earlier.  To break free, the young adult used its strong mandibles to burrow a hole.


By 16 April, 5 young adults broke free.  It was a shame that I did not witness the young adult emerging from its pot.  I was determined to do so I waited on 18 April to see some action.  I was disappointed.  As I turned the pot around, I found another opening.

The 6th and 7th young adults had emerged from the other side of the pots! Just as I thought the openings would be aligned vertically, similar to the other 5 young adults, I was wrong.  The 8th young adult emerged on the other side around 27 April 2010 right beside the 4th hole.  Indeed, they were like playing hide-and-seek with me.



I had one last chance to witness the emergence of the young adult Potter Wasp.  However, between 28 April and 11 May, there were no further developments.   I made some rough calculations thereafter. Pot #9 was completed by 31 March and small caterpillars were found in the pot. I left for Fraser’s Hill at 0400 hrs on 1 April and one of the caterpillars head was sticking out of the opening.  When I return on 4 April, the opening was closed.  If the incubation period was roughly about 25 days, it should have emerged by end of April.  I began to think that it could be “stillborn”.

On 28 May, I decided to give it a little tap.  I probably applied too much pressure and it broke the pot!  Oops!
Well, I guess it was a blessing in disguise too.  Otherwise, I could have waited forever and ever to know the hidden truth.  The pot was empty!All I found was some dried up “poo”. There were 9 pots but only 8 young adult Potter Wasps.  Now, was there a larva in the 9th pot in the first place?  If not, why did the Potter Wasp build an empty pot? I have to say it was mind boggling and intriguing till the end …

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