There are a number of different paper wasps to be found in Hong Kong. Paper wasps are vespid wasps that gather fibers from dead wood and plant stems, which they mix with saliva, and use to construct water-resistant nests made of grey or brown papery material.
Our word for today is 'petiole', which in entomology is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, and wasps in the order Apocrita. This term can also refer to a constricted stalk, such as that which anchors the nest. Often paper wasps only prey on caterpillars, but this one will also attack and capture other insects like grasshoppers, or dragonflies.
You can see this one making part of the nest in his mandibles, The nests are typically round, with no protective envelope, with cells facing downward.