1. Why Different Hornet Species Build Nests in Different Places in the Same Town
Even within the same neighborhood, different hornet species live in different places. For example, the Kogata-suzumebachi often builds nests in the thick branches of garden hedges or trees, and they can also be found under the eaves of houses [2]. Other species have different preferences. The O-suzumebachi typically builds nests in the ground, such as in hollow spaces at the base of tree roots [1]. The Kiiro-suzumebachi is very flexible; it nests under eaves, in attics, on cliffs, or in tree branches [1]. The Hime-suzumebachi prefers closed spaces, such as under floors, inside walls, or in storage sheds [3]. The Kuro-suzumebachi also usually nests underground [1]. This means that underground nests are not exclusive to the O-suzumebachi.
However, local government documents describe these as "common places," not strict rules. There are rare cases where O-suzumebachi nest in attics, or where Kiiro-suzumebachi nest in tree hollows or underground [1]. These locations are trends, not absolute laws. So, how widespread are these trends across Japan?
2. How Many Hornet Species Exist Worldwide and in Japan, and Where Do They Live?
The hornets (Vespinae) include 61 species worldwide and 16 species known in Japan. They are distributed from flatlands to low mountains across the entire country [5]. Note that the number of species can vary depending on how they are classified; for instance, Kobe City’s documents list 17 species [3]. Generally, hornets build nests in a wide variety of places, including tree branches, tree hollows, rock faces, under house eaves, in attics, and underground [5]. Because they live from flatlands to low mountains, their habitats overlap with towns and villages where people live. The fact that house eaves and attics are included in nesting sites is likely related to this overlap with human settlements.
Given the effort it takes to build these nests, are they reused the next year?
3. Why Hornet Nests Are Used for Only One Year and How New Queens Survive Winter
Inside a nest during winter, there is nothing left. A nest is used for only one year and is never used again the following year [3] [4]. So, where do the hornets that survive the winter go? It is only the new queens. New queens leave the nest and spend the winter alone in small gaps, such as in stone walls, inside rotting wood, or underground [3] [5]. The old queen, worker hornets, and males die before winter arrives [3].
This means that in winter, hornets are not huddling together in the nest for warmth. Instead, a single new queen survives alone in a small gap outside the nest. The gap she finds becomes the starting point for the next year. What does the queen do when she wakes up in spring?
4. How One Hornet Queen Builds a Nest of Hundreds of Hornets by Summer
In spring, the queen who survived the winter wakes up and begins building a nest alone. The timing varies by region and source; Nagoya City documents say it starts around April or May, while Kobe City documents say around June [1] [3]. As summer turns to autumn, the nest grows larger as more worker hornets are born. The number of workers at the peak varies by species: about 100 for the Kogata-suzumebachi, several hundred for the O-suzumebachi, and it is not rare for the Kiiro-suzumebachi to have over 1,000 workers [1].
The size of the nest also differs by species. Sendai City documents describe a Kogata-suzumebachi nest as 15 x 20 cm and a Kiiro-suzumebachi nest as 40 x 60 cm [2]. If you multiply the length and width, the apparent area is about 8 times larger for the Kiiro-suzumebachi. The difference in worker numbers is about 10 times, which seems similar to the difference in nest size. However, this calculation compares numbers from different sources, so it is not a direct comparison under the same conditions. A nest that started with one queen becomes this large. Can species with such large nests live in paved city areas?
5. Can O-suzumebachi Hornets Build Nests in Paved City Areas?
Chiba City Public Health Center documents state that O-suzumebachi build nests in the ground and "cannot live in paved urban areas" [4]. This sentence does not mean there are zero O-suzumebachi in the city. It means that because they build nests underground, they cannot do so if the ground is covered by concrete or asphalt. However, this specific statement is found only in the Chiba City documents among the sources reviewed here. Other local government documents mention nesting in the ground, tree hollows, or rarely in attics, but do not discuss paving [1]. Therefore, it is best to view this as a perspective from one specific source.
What is certain is that because nesting locations differ by species, the places where they can easily live differ even within the same town. These places include soil in gardens and parks, hedges, and under eaves.
6. How to Draw and Compare Where Different Hornets Build Their Nests
Try drawing the "addresses" mentioned in this article in your notebook. Draw one picture for underground spots, one for garden tree bushes, one for under eaves, and one for closed spaces like under floors or storage sheds. Then, list which species commonly builds nests in each place. You might see the scenery of your town differently. Safety Note: If you find a real nest or hornets, do not approach or touch them. Look from a distance and tell an adult or your local government. Although winter nests are empty, never approach them.
If you want to learn more, check your local government’s website for pages about "hornets." These pages may list the common species and nesting sites in your area. The local government documents used in this article are examples of such pages.