Their work usually starts in the 10th lunar month. Restaurants in the central province pay VND150,000 ($6.5) for a 20-mm, pupa-like insect.
Common termites nest in the ground and the nests are taller than the surroundings.
Besides identifying where the termite is by their mounds, the catchers have another way. The worker termites eat the leaves and make noise in waves which sounds almost like a light rain.
Termites live in a hierarchical social group with queens, kings, workers, and soldiers. Workers make up of the largest numbers in a colony. They look after the king and queen, tend the young, build and repair the nest, and feed the soldiers.
Each nest usually has one or two queens, each about 20 mm long. They resemble a pupa with a small head and a big belly.
Chung Van Luong of Ngoc Lac District, Thanh Hoa said catching termites only requires simple tools but also experience. "When you see the mound rise high it means there are termite queens inside."
Termite nests are often built with interconnected floors. "The queen is responsible for reproducing, so all the remaining termites work hard to build a nest and feed the queen," Luong said.
The queens live on firm blocks of soil like this surrounded by many black termites (larger than the workers) and white ones.
Termites are often found at the foot of large walls or in tree barks, making searching and digging for them difficult.
Luong said: "If we are lucky, we can dig up 10 new termite nests every day and get about 15 termite queens. Each fetches VND150,000 ($6.5)."
Termite queens are considered protein-rich and restaurants cook them in various ways such as roasted, stir-fried and steamed. Some people also make alcohol out of them.