Let's talk about termites.
Let's talk about termites
Termites are usually classified based on their lifestyle and moisture requirements, rather than into a single rigid list of individual species (there are about 3,000 worldwide).
The four main groups are:
Subterranean termites (Rhinotermitidae) are the most common and harmful group worldwide. They live in the soil and require contact with groundwater. Well-known genera include Reticulitermes (common in Europe and North America), Coptotermes (including the highly destructive Formosan termite Coptotermes formosanus), and Heterotermes. They build mud tunnels to reach wood from the ground.
Then there are drywood termites (family Kalotermitidae). They live entirely inside the dry wood itself and require no contact with the soil or an external moisture source — they obtain their moisture from the wood and from their own metabolism. As a result, these are precisely the species you might find in furniture, roof structures, floors, and building beams. Important examples are the genera Cryptotermes, Incisitermes, and Kalotermes flavicollis, which occur in the Mediterranean region. Approximately 15 percent of all termite species can be classified as drywood termites.
Moistwood termites (including Archotermopsidae, with the genus Zootermopsis) live specifically in wet, rotting, or damp wood, such as dead tree trunks or timber affected by leaks. They appear in homes primarily where a moisture problem already exists.
Higher termites (Termitidae) form the largest family but are mainly tropical. Many of them are the well-known mound builders and fungus cultivators; these are less relevant for homes in temperate regions.
Termites and structural timber
In practice, there are two significant drywood termites in Europe that can live in structural timber, plus a few borderline cases.
The yellow-necked drywood termite (Kalotermes flavicollis)
This is the only drywood termite that occurs naturally in Europe. Its distribution area is around the Mediterranean region: Southern Europe, North Africa, and the Middle East, plus it has been introduced to the Azores. It is the species found in Dutch olive trees in 2025. Originally, the species primarily attacks deciduous trees, fruit trees, and vines, but in Southern Europe, it is also known as a pest in wooden structures — particularly in churches and museums, where it eats away at both load-bearing beams and wooden objects. Regarding CLT: the material is in principle suitable dry wood, but this species has a distinct preference for hardwood, whereas CLT is almost always made of softwood (spruce/fir). This makes softwood CLT a less obvious target.
The West Indian drywood termite (Cryptotermes brevis)
This is the most notorious drywood termite in buildings worldwide, and the most destructive in dry structural timber. The species does not occur naturally in Europe but is an invasive alien that hitches a ride on furniture and wood. In Europe, it is established in the Azores (Portugal), where it is considered the most damaging drywood species and can form hundreds of small colonies in a single piece of wood. It has also been sighted in Italy. This species is, in fact, a typical inhabitant of structural timber, furniture, boats, and wooden objects, and tolerates very low wood moisture levels. Of the European drywood termites, this is the one that could best survive in dry softwood construction material such as CLT. However, it remains rare and localized in continental Europe.
Dutch situation
In 2025, a colony of the yellow-necked drywood termite (Kalotermes flavicollis) was found for the first time in the Netherlands — indoors, in a dead part of an old olive tree originating from Southern France. DNA analysis pointed to this origin. This species prefers hardwood. It is the first drywood termite and the fifth termite species to be identified in the Netherlands with a vital colony. This species is originally widespread along the Mediterranean coast in Southern Europe, North Africa, and the Middle East, and lives hidden in dry (dead) wood of fruit trees, vines, and wooden structures. The alates (winged breeders) are recognizable by a yellow neck, yellow legs, and antennae that contrast with a dark brown head and body.
Important to note: there is no indication that this imported colony has established itself further or spread in the Netherlands. However, according to the researchers, it is likely that the species was introduced in more places via Mediterranean plants.
Reproduction and dispersal
The natural dispersal of drywood termites is surprisingly slow and over short distances. This stands in sharp contrast to how they travel across the world in practice — namely, hitching a ride on human trade.
How they do it: the swarm flight
A colony disperses via winged reproducers, the alates or "swarmers." Only when a colony is mature — for drywood termites, this usually takes about five years — does it produce these winged animals. At a suitable moment (warmth, often a specific season), they leave the nest simultaneously. This simultaneity is no coincidence: synchronous swarming increases the chance of finding a partner and reduces inbreeding.
The process is always the same: the alates fly up, mate, and shed their wings shortly after landing. A mated male and female search together for a suitable spot in dry wood — a crack, crevice, knot, seam, or nail hole — crawl inside, and establish a new nest. That pair becomes the king and queen. Most swarmers do not make it to this stage; they are eaten by birds, ants, and reptiles, or they dry out.
How far: not far under their own power
Drywood termites are poor flyers. They do not flutter purposefully over long distances, but mainly let themselves be carried along by the wind. As a result, they usually do not get far from their starting point. For the western drywood termite (Incisitermes minor), it is explicitly described that the alates do not move far from their point of emergence precisely because of this. Research into invasive termites confirms the broader picture: dispersal in natural habitats is slow, due to the combination of long generation times and the short flight distance of the alates.
Concrete distance figures vary by species and are highly wind-dependent, but it generally involves tens to at most a few hundred meters — not kilometers. Often, an infestation even spreads within the same building or the same tree: alates from an existing colony simply seek out a new crevice nearby and establish a satellite nest there. A house can thus harbor multiple independent colonies.
What is the likelihood that structural timber, and particularly CLT, will be affected?
A drywood termite establishes a new colony when a mating pair crawls into a crack in exposed wood following the swarming flight. If there is a solid facade (for example, a masonry outer leaf or closed cladding) in front of the wooden structure, that wood is shielded from direct landing and colonization. The swarmers simply cannot reach the load-bearing wood as long as there are no openings leading to it. In this sense, a well-sealed facade reduces the chance of a new infestation via the air. This aligns with the fact that these termites are poor flyers that do not travel far: if they land at the facade but cannot find access to wood, they dry out or are eaten before they can establish a nest.
This is important in relation to residential construction. The realistic route by which Kalotermes flavicollis enters a home here is not through swarmers penetrating your facade from the outside — the outdoor climate barely supports free-swarming colonies, and the species has been found here almost exclusively via the import of infected wood (olive trees). A facade with a cavity and insulation in front therefore provides good protection against the already small risk of colonization from the outside. It does not protect you against wood that entered the structure already infected, but that scenario is highly unlikely with regular, dried, and certified construction timber. Specifically for CLT constructions, it is good to bear in mind that it is softwood, and Kalotermes flavicollis prefers hardwood.