The West Indian Drywood Termite- Genus Cryptotermes

I. History

The West Indian drywood termite is of significant economic importance. It is a species that is responsible for considerable property damage in Hawaii.
Its origin is unknown. Considering that the earliest ships arriving in Hawaii were made of wood, as were their cargo crates and barrels, its introduction has probably been repeated numerous times. This drywood termite was first reported in Hawaii in the 1860's. It is scattered over much of the southern continental US, the Pacific Rim, and in the Caribbean where it is a serious pest, especially in Puerto Rico. It is distributed throughout the Hawaiian Islands. This termite is much more transportable than the ground termite but its damage is considerably less. This is due to the fact that it reproduces much slower and has significantly smaller colonies. Its presence should not be ignored as it is capable of serious damage if left unchecked.

Drywood termite droppings
The color of the droppings from drywood termites is dependent not only on the type of wood they are eating but the part of the wood and, I believe, the individual termite. Here we see two distinctly different colors of termite droppings coming from the bottom of the same four-by-four post. This was an active infestation in an older house in Manoa. The age of the dropping has nothing to do with the color as is commonly believed.

Drywood termites were infesting several ceiling beams in a townhouse. The beams were about two feet above this shelf and the droppings bounced as they hit. Again, note the variation in color.

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II. Caste System
The West Indian drywood termite is not a true social insect, as it does not have distinct caste members to perform specific functions within the colony. Its system consists of a royal couple, a king and a queen, usually the founders of the colony. There are also soldiers and nymphs. There is no true worker class. The nymphs serve as workers until they develop into alates (winged reproductives) when they will swarm in search of establishing a new colony. Supplementary queens may also develop.
The function of the royal pair is procreation. Once the bridal chamber is constructed, mating will take place. During the first three months the queen lays only two to four eggs. These take approximately two months to hatch. The eggs are pink and shaped like jelly beans. These take approximately two months to hatch. The nymphs have to be fed predigested food from the adults as they are not born with the protozoa (primitive unicellular animals) necessary to digest cellulose. Protozoa secrete cellulase which breaks down the cellulose into simpler materials capable of being digested by the termites. Such a relationship, where two dissimilar organism are intimately associated together for their mutual benefit, is known as symbiosis (Hickin, 1948). Protozoa which are utilized by the West Indian termite are Foaina humilis Kirby (1942), Devescovina striata Foa (1905), Tricercomitus divergens Kirby (1930), Hexamastix conclaviger Kirby (1930), Calonympha sp. (probably C. grassi Foa, (1905) (Zimmerman, 1948).
The king and queen will rear only the first group of nymphs until they can feed themselves. Subsequent eggs and young will be cared for by the older nymphs. During the first year the queen will lay eggs only for the first three months then waits several months before laying again. In time, the queen develops a distended abdomen to facilitate her egg-laying. The king is there to fertilize her when necessary. The development of the West Indian colony is very slow. After about a year, the colony contains only about a dozen termites.

Other than the royal couple, the soldiers are the only members in the system that have a specific function. Soldiers are produced after the first year. Their task is to protect the colony from invaders, which in most cases are ants. They are totally dependent on the nymphs for their food, as they are unable to chew food and feed themselves.
The nymphs perform the duties of workers by foraging, feeding the queen, king, soldiers and the young, and sealing up holes with masticated wood. If the primary reproductives are lost, they can be replaced by several nymphs as secondary reproductives. Although the total reproductive potential of secondaries can exceed that of the primary king and queen, these colonies require a long period to reach a size that can do significant damage.

When the workers have developed into alates, they take to the air when the conditions are good to start their own colony. Swarming is the primary way the termite naturally spreads after it has been transported to a new area. Spread by swarming is slow, however, because the termite is a poor flier. Unassisted, it cannot fly more than 1/4 mile. Moreover, the swarmers are attracted to the closest light source.

Swarming usually takes place in June and July but the occasional swarmer can be found at any time of the year. Swarming usually takes place after sundown between the hours of 7:00 PM and 9:00 PM. This can vary. Swarming takes place when there is virtually no wind. During the swarming season the termites will open their flight slits (slits in the side of wood open to the air) and poke their noses out to see if the conditions are right. If the wind exceed 2 mph, then the swarming will not occur. If swarming starts and the wind increases to more that 2 mph, swarming stops. They will then seal the slits with masticated wood and wait for another time.

If the conditions are favorable though, all the alates will leave the colony in a matter of a few minutes and flutter about. Once swarming begins it is usually completed within thirty minutes. At this point something remarkable happens. These insects which spend their entire life in the dark and avoiding the light are now attracted to any light source. Perhaps it is their way of finding each other. After a brief time they drop to the ground and shed their wings. They then go about looking for a mate. Once they are paired off they move around in tandem, with the male following the female. They then look for a place to begin their colony. Fortunately for us, most of the swarmers are eaten by birds, toads, ants, geckos, spiders, or chameleons. Only a very small number survive, perhaps 1 to 2%.

Since they are usually on the ground it is easy to see why they often end up in doors, this being the first piece of wood they come to and the bottoms are untreated and often with holes which allow then access. They like plywood for the same reason that it has holes already in it. They are not deterred if there are not holes in the wood for they will simply chew their way in. At this point they are not eating the wood but chewing it and leaving the pile of undigested wood shavings on the floor. I had the stairs in my home changed to oak. The carpenter drilled small holes in the oak then pounded finishing nails into these holes then filled them with wood dough. One night during construction I noticed a small pile of fine dust outside one of the drill holes that had not yet been filled. With a light and hand lense I watched as two drywood termites crawled in and out of the hole chewing a small amount of wood and bringing it to the top of the hole and depositing it at the opening. They did not eat the wood. They worked tirelessly excavating a new home for themselves at a steady pace for over an hour until I ended their work.

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III. Habitat
The West Indian termite likes to make its home in most kinds wood in houses and buildings. Our most common building materials are Douglas fir, oak and redwood and woods like Koa, maple, walnut and other hardwood for cabinets and furniture and all are readily infested. It will bore through books, tarpaper and other material containing cellulose. Since it does not require a source of water for survival, it can be easily transported throughout the world. It infests packing cases, crating lumber, picture frames, boxes, barrels, and wooden articles. In founding a colony the reproductives take advantage of any small crack, joint or hole which they can find and commonly begin their tunneling from such a point. After penetration is accomplished, the male and female tunnel along the grain of the wood, establish a nest and the female lays a few eggs. When the tunnels become crowded, an exit hole or "kick-out" is bored to the exterior and quantities of the fecal pellets are pushed out. When they are finished, they then seal up the hole with masticated wood. Fecal pellets are loose and uniform in color, varying from beige to very dark brown depending on the type of wood consumed. This habit makes the presence of the termites known and is usually the first indication that an infestation exists in any article or situation. The infestation is usually easy to locate directly above any pile of pellets. In houses and other buildings, infestation frequently begin in attics, and spreads to all parts of the structures. Proper screening of all attic openings with a fine mesh screen will aid greatly in reducing infestations.

This termite works in much smaller colonies and much slower than does the Formosan ground termite. In well-established colonies the number of individuals rarely exceeds 300; in heavily infested wood, however, colonies may unite, resulting in higher total numbers (Yates-Urban Press). This drywood termite does not cause great damage in short periods of time. Its action is gradual and cumulative but persistent.

With the exception of the winged stage of the reproductives which fly in the light for, at most, a few hours and also with the exception of the harvester termites of the subfamily Hodotermitinae, termites live their lives in the dark, reacting strongly against the light. This is probably one of the ways in which termites have successfully resisted desiccation and is achieved by the use of tunnels in the wood and by the covered runways by means of which the termites are able to control the temperature and humidity of the microclimate within their living space (Hickin, 1971).

With the exceptions given above, termites are blind, so that in finding their way about they must rely on senses other than sight. Indeed, it has been discovered within the last few years that termites possess a sense of smell sufficient for them to distinguish between odors which are acceptable and which attracts them and odors which are not acceptable and repel them. It has also been discovered that termites of the same species are able to communicate with each other in a primitive manner by the laying of scent trails which attract other termites to follow along the same trail. These secretions are known as pheromones and there is no doubt that these trail-laying substances play an important part in the activity organization of the colony. There seems no doubt that this means of communication using chemical odor reception and we must keep in mind that this is taking place entirely in the dark-prevents wandering, dispersal, the intrusion of other species, and perhaps predators.

Drywood termite droppings
The drywood termite colony lives in the piece of wood that also serves as its food source. They have no source of moisture other than the moisture content of the wood which in Hawaii is about eleven percent. Therefore, it is important they retain all of their fluids. To facilitate this they have absorbent pads in their lower abdomen that remove the water in the droppings before they are excreted and keep the termite hydrated. The termite droppings are very dense, hard and somewhat oval shaped. When examined closely small grooves can be seen caused by the muscles in their abdomen when they were being formed. Droppings will generally be the same size and shape but color may vary.

Occasionally debris from ants will be confused with that of termites. The debris from ants is not necessarily their droppings but just bits of material they are moving to clean their dwelling. It is irregular shaped and for the most part is very fine. If ants can gain access to a drywood termite gallery they often make their nest in it and will push out termite droppings. This is frequently the case after a house has been tent fumigated.

The droppings are allowed to accumulate inside the termite galleries until, apparently, word is passed that it is time to clean house. At this point a small ‘kick-out’ hole is opened from the gallery to the outside and with a collective effort all of the termites will gather the droppings, one-by-one, and push them out the hole. I have observed this behavior on a number of occasions and as quickly as one dropping falls from the hole another tiny termite head appears with a dropping in its mouth and it too tumbles out. The process continues until the foreman decides enough cleaning has been done. At that point wood will be chewed into a paste and the hole is plugged. The paste dries into a brown, brittle door, about as thick as a piece of paper that keeps out small predators such as ants. They may open this hole again at a later date to continue cleaning or open a hole in a different location. Frequently people see a pile of dropping only once and falsely assume the termites have either died or moved away. If they open a ‘kick-hole’ in the wood and find a piece of sheetrock, hardboard siding or other wall covering they will eat through this material as well. They are not necessarily digesting this material, just chewing through it.

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