Drywood termites are a group of termites that build their nests within moisture-free wood. They belong to the Kalotermitidae family (as are some dampwood termites) spanning several genera, and are considered primitive termites. Drywood termite genera include Cryptotermes, Neotermes, Glyptotermes, Incisitermes, and Kalotermes, but the most distinctive and widespread is probably Cryptotermes. Drywood termites are sometimes called powderpost or furniture termites due to being found commonly infesting furniture.
There is similarity between drywood and dampwood termites in that both nest inside wood. But unlike dampwood termites, which require moist wood in which to nest in, drywood termites need wood that is dry, and therefore, have adapted well to human habitation, finding an ideal habitat in the dry wooden frames, beams, and furniture in homes and buildings.
Living inside wood that has no contact with water, drywood termites have this curious ability to metabolize water from the wood that they eat, absorbing and reabsorbing water from their feces, as needed. In humid conditions, drywood termites will excrete liquid feces, but in dry conditions, they reabsorb the moisture in their intestines, and excrete their feces as pellets (which are called frass). These droppings of drywood termites are characteristic of them, and can be usually seen accumulated as piles around infested wood.
Above – Drywood termite pellets or droppings, called frass.
The typical drywood termite colony
Drywood termites colonies are small, usually under 1000 individuals. The workers are usually whitish, slow moving, and long bodied. In most genera, the soldiers look quite typical of most termite soldiers, but Cryptotermes is different. The soldiers have a small stub head (phragmotic head) and short mandibles, with which they use to block tunnels against intruders.
Above – Drywood termites (Cryptotermes spp), with winged alate, workers, and soldiers.
Above – A drywood termite soldier of Cryptotermes with phragmotic head.
The king, queen, and nymphs are all mobile and able to move within the nest, which is relatively simple in structure, usually consisting of numerous galleries and chambers within wood. The queens are only slightly physogastric (enlarged abdomen) which allows them to be mobile.
Above – A simplified diagram of how a drywood termite nest in a block of wood looks.
Above – The typical nest structure of drywood termites (Cryptotermes) in side view.
The insides of the galleries and chambers are often filled with their droppings, especially in old nests. Along the wood surface, tiny “kick holes” open up to the outside, through which the termites periodically dump their droppings. Once the wood becomes too damaged, the colony gradually migrates to any connected/adjoining wood.
The damage wrought by drywood termites is slow, and it takes years before their presence is noticed. A single colony that nests in a piece of wood will often just inhabit and eat out this single piece of wood, leaving adjoining areas untouched. Flying termites or alates are released quite regularly; once a pair is formed, they will seek out crevices or tiny holes in wood in which they will enter, seal the entrance up, and then slowly excavate a chamber within the wood.
Secondary reproductives
A strong characteristic of primitive termites (like drywood and dampwood) is their ability to produce secondary reproductives. This phenomenon is also called neoteny, and for drywood termites, may be a trait brought on by their evolutionary circumstances.
In the wild, drywood termites normally nest in the branches of dead trees. They can safely nest there for years, but normally things don’t work so smoothly in the wild. In the event the branch or tree falls and drops to the ground, the colony is split up; most of the time, other termites will move in and quickly devour the branch, leaving the remaining drywood termites with a slim chance of survival. Thus, the ability to rapidly turn into reproductives may increase the survival odds for what remains of the colony in this situation.
Above – Drywood termite workers, or pseudergates.
In Cryptotermes species, it appears all the workers are not really “workers” per se, but actually pseudergates possessing wing stumps and able to turn into fertile reproductives given the right circumstances. Colonies are constantly producing winged alates that often disperse in small groups.
Above – The pseudergate nymphs of drywood termites already have poorly defined wing stumps, indicating their ability to turn into fertile adults under certain situations.
Above – A drywood termite worker, or pseudergate, viewed close up.
Above – A drywood termite alate or reproductive, that has shed its wings.
Many drywood termite species have been inadvertently spread by unsuspecting humans due to the transcontinental movement of furniture or wooden boxes that contain small or splintered colonies. In some regions of the world, drywood termites are considered a serious pest, although their damage is still nowhere on the scale of certain subterranean termite species. Nevertheless, they can still cause serious damage if left undetected for years.
Drywood termite control methods
The methods for controlling or treating drywood termites are not the same as for subterranean termites. What works for subterranean termites usually will not work for drywood termites; and vice versa. However, control of drywood termites is easier due to their nests being much easier to locate. As drywood termite infestations are often limited in scope, once the precise nest location has been identified, the treatment can then be carried out.
Above – Drywood termites are usually slow to cause damage, but given a few years, are able to severely damage a piece of wood.
Some of the control methods employed for drywood termites:
- Orange oil termite treatment. This method is fairly safe, and environmentally friendly.
- Fumigation. Only meant for large scale infestations involving multiple colonies in a house.
- Heat treatment. This involves pumping hot air via propane heaters into infested wood and maintaining it long enough to eliminate the infestation. Currently limited in use.
- Microwave treatment. Similar to heat treatment, and involves utilizing high temperature from microwave devices. Usage is limited.