This is the largest Polistes paper wasp in Hong Kong, Taiwan and, in fact, the whole world!
Polistes gigas is a truly impressive wasp, and seeing one in its natural element can be unforgettable. Females average 30 to 34 mm in body length, occasionally reaching a maximum of 38. It is a uniform dark brown in colour, with a reddish tinge under strong sunlight. The wings are smoky brown. The legs are extremely long; this is obvious when the wasp is in flight, since the legs are usually dangled vertically. The flight is slow and distinctive, with a very loud, low buzzing. This species is unusual in that the male is distinctly larger than the female, sometimes exceeding 50mm in length! He also has a greatly enlarged head with extremely strong, sickle-shaped mandibles which can easily draw blood!
Polistes gigas is in fact quite widespread in Hong Kong, being found throughout the New Territories as well as Hong Kong Island. Although easily noticeable due to its conspicuous size and appearance, colonies are usually quite small, usually with less than 20 wasps, and thus not so easy to locate by looking for a flight path. It can often be found in urban parks and even residential estates, where it nests in trees and thanks to the nest being hidden well among the foliage and low activity, often go unnoticed, successfully completing their colony cycle. The nest is a typical Polistes nest but very large, with relatively few cells; the cells are very broad and deep. The cells containing male larvae get far longer and broader, and the pupal cell caps are very long. Male cells are usually produced only towards the end of the colony cycle, and since new cells are constructed outwards on the outer edges of old ones, mature nests of this species can be quite queer in shape, with the outer cells far longer and wider than the inner ones. Nests are almost always built in very dark locations; they can be found in abandoned houses, trees with dense foliage, tree hollows and even nesting boxes installed for birds.
Above: A nest found in an abandoned house.
Below: A nest in a tree.
Polistes gigas preys mainly on large caterpillars. Despite its fearsome appearance, it is a most unaggressive species near the nest site, and will almost never attack unless severely provoked. When colonies are small, the wasps flee the nest upon disturbance. However, a larger colony with brood will defend the nest and sting upon severe disturbance, and having been on the receiving end of its sting, I can only say it is exceedingly painful! I say this after comparing with a few species of Vespa, other Polistes, Parapolybia, the common honeybee, Xylocopa, some large Sphecids and a large Pompillid. The pain is rather excruciating and the resulting swelling and redness was quite severe too, lasting more than 8 hours. Therefore, one would be wise not to deliberately provoke these wasps. However, their nests can be safely left alone and should not be destroyed.
Also of interest are the males. Their enlarged size and greatly enlarged head and mandibles are really extraordinary. When I caught my first male specimen, I was so impressed with his size, but thinking he was harmless like any other male, I restrained him for this photo. However, he struggled continuously, and his sheer strength was incredible. At one point, he managed to turn his head and immediately clamped his mandibles down on my finger, causing a surprisingly deep cut that bled for some time!
At the same time, I also witnessed some intense fighting between males near their nests. I was not able to tell the reason behind the fight, or whether the males came from the same colony or elsewhere. The fights reminded me of stag and scarab beetles; they tried to throw each other off a branch, sometimes inflicting serious injury on their opponents.