Incisitermes minor is a species of termite in the family Kalotermitidae known commonly as the western drywood termite. It is native to western North America, including the western United States and northern Mexico. It has been found in many other parts of the United States, all the way to the East Coast. It has been reported from Toronto.[1] It has been introduced to Hawaii.[2] It has been noted in China and it is not uncommon in Japan.[1] This is an economically important pest of wooden structures, including houses. In California and Arizona alone its economic impact is estimated to be about $250 million per year.[1]
Within a single colony there are three types of termites, the alates, soldier, and worker. This eusocial species is a dark brown color and has an orange head.[1] The colonies are most active during the spring and summer, preferring to be active in higher temperatures.[3]
Morphology
There are three types of termites within the colony: the alate (swarmer), the soldier and the worker. Alates have an orange-brown head and pronotum, an 11–12.5mm long, dark brown abdomen. This is the only caste that leaves the colony, which happens when they seek a mate. If they are successful, they will form the new kings and queens.[1][4] There are also soldiers, which are large, reddish-brown, and have two teeth visible on the left mandible. They are noted for having a larger third antennal segment. They are 8–12mm long, and can weigh from 20 to 25mg.[1] This eusocial species does not have a normal worker caste. There are "pseudergates" which are false workers characterized by their lack of wing pads, as well as "nymphs" which do possess wing pads. These wing pads allow the nymphs to molt into a soldier or an alate, because they are not sterile. These workers are not the bottom class, meaning they are capable of becoming soldiers and alates.[1] The pseudergates group is also able to change into male or female alates just by molting, which is very different from other insect species.[5]
They are dark brown and have an orange head. The soldiers are larger than the alates, and they reach an average length of 0.4 inches, and have a broad red head with black mandibles. They have a larger third segment as well.
It is able to persist in other climate types, as evidenced by its isolated occurrences across North America, including many in Florida, and its establishment in Japan.[1]
Termites swarm in order to reproduce. This is when large groups of the termite gather in a specific location to mate, before going separate ways to establish colonies. The alate group engages in the swarming behavior. The alate group swarms in late September through November in Southern California. On warmer days, the termites will swarm earlier in the day.[1] Swarming occurs on days with temperatures between 26.7 and 37.8°C (80.1 and 100.0°F). The alates emerge from inside the wood nest, and as they reach the outside they will take off. The alates are not able to fly well, and therefore do not move far from their emergence point. When they land, they remove their wings and crawl around (wingless) to find a mate. Once a mate is found they engage in courtship activity.[1] In finding a mate, the females crawl with the male behind. Once the female accepts the male they are now mated for life, and are now the king and the queen. In order to begin a colony, the male and female have to find a piece of wood with a hole in it, which they will enter and create a royal cell.[1] This whole process can take three to four days. When they are done excavating they have to plug the hole with gut contents.[1]
Afterwards they enter a long period of inactivity, for approximately nine months; during this period the queen will begin to lay eggs. After nine months the eggs are hatched and the queen and king feed them until they can begin to excavate the wood.[1] Eventually the new termites will be able to consume wood on their own. At this point they will be a wingless worker caste that will forage and begin to feed the next generation of new termites. They are the ones that damage the wood as they eat and digest it to feed and take care of the nest.[8] In the next two years as more eggs hatch, the king and queen have a small colony, including a soldier and probably a dozen or so nymphs. Each termite has seven instars, which are different developmental stages after which they shed their skin and assumed different body forms. It can take about a year for the termite to go from egg to maturity.[1] With time the females undergo physogastry – where the ovaries enlarge and the abdomen swells. The kings look the same as when he dropped his wings.[1] As the colony matures and workers mature, they will become either soldiers or reproductives. The reproductives will be the new swarmers will exit the wood to form new colonies. Those alates will then go on to mate and form their own nests.[8]
The colonies are slow growing. It can take five to seven years before there is visible damage in the wood from feeding. There are also secondary reproductive pairs that can appear, but it is very rare. There are only multiple pairs if it is a mixture of two different colonies.[1]
Behavior
Like other termites, this species is eusocial, living in a colony with a caste system. There are different types of adult insect: the alate, or swarmer, the soldier, and the pseudergate. The alates are the swarmers, and they can be male or female.[1] The eusocial groups are important because it allows them to have multiple generations that can take care of the young. It also allows for specialization, so that there is a specific class that can be best suited to defending the nest and other which are better at foraging.[9]
Food gathering
The termites feed on wood and excavate very similarly to other termites. Their feeding behavior results in larger, more cavernous, irregular evacuations. I. minor also excavates toward the outer edge of the food, but it does not break the wood. They accomplish this by leaving a thin, outer layer, which is protective. This often gives the wood the appearance of being strong, but it is still weakened from the eating on the inside.[1] The termites are also known to feed on dead tree branches, and not just feeding on live trees.[10] There is also a feeding hierarchy within the colony. In an experiment, filter paper was marked with Rb (Rubidium) to show that not all the termites in the colonies feed. The analysis of the Rb levels indicated that in the hierarchy the nymphs are the primary donors, the primary eaters, and the larvae are the primary recipients. This experiment is able to show this because those that directly eat the Rb labeled filter paper have a higher concentration of Rb in their body than those termite that are eating the food second hand after being fed. The alates might also require more care before swarming.[11]
As the termites eat, they leave very little signs that they are present in the wood. However, they do have a small hole on the surface of the wood through which they eject their fecal pellets. The fecal pellets are hard, and evenly shaped, and found in conical piles or scattered on horizontal surfaces. The fecal pellets have the same hydrocarbons as the species of termite, and each termite has unique cuticular hydrocarbons.[12] Many other species of termites have bacterial and fungal loads that exist with the colonies, but I. minor prefer drier forms of wood have very small bacterial and fungal microbial loads.[13]
The termites do have a preference to the type of wood that they like to consume. The termites are most likely to eat wood that is not tainted with repellent chemicals in the wood. The termites are also more likely to consume wood from which the colony has developed. The Douglas fir is the most popular wood that the termites like to consume. Termites that were exposed to extracts of least-preferred wood have a slight increase in mortality, indicating that the type of wood is important for survival.[14] The strain of wood that was least preferred was a strain of commercial timber called Karamatsu wood. This strain experienced the lowest loss in mass and is therefore considered the most resistant.[15]
Activity levels
The termite's activity is associated with the temperature. Termite activity is highest during the spring and summer. However, an increase in temperature, even in the winter months, can cause an increase in activity. Activity is also lowest during the morning, peaking in the later afternoon. There is a very strong correlation between the temperature and the activity of the termites. As there is an increase in temperature there is an increase in activity.[3] As the termites are more activity, they have an increase in the release of CO2.[16]
Impacts
This species is probably the most destructive of the dryland termite species in the western United States,[6] while rhinotermitidae subterranean termite damage is more costly.[12] The western subterranean termite (Reticulitermes hesperus) is considered to be the worst termite pest in California, with I. minor in second place.[17]
This is a picture of what wood looks like after it has been eaten by termites. The inside is full of holes, so the strength is compromised.
In Southern California, it is estimated that this species represents about half of all reports of wood-destroying organisms, and much more closer to the coastline. Urban sprawl will likely increase populations.[1]
It will also probably continue to spread to new areas. It was discovered in the historic New Orleans building Perseverance Hall in 1999, where it was probably introduced in furniture shipped from the west.[10] One common vector of introduction is the boat, such as the yachts and other craft that launch from Southern California. The termite was noted in Australia after having been inadvertently delivered by boat.[18]
Management
As a pest of human habitation, this termite has been the target of many pest control methods.
In severe infestations a structure may be tented and fumigated with sulfuryl fluoride. This generally kills all the termites in the structure. Less extreme spot treatments can be made by drilling into the gallery and injecting pesticide,[1] such as pyrethroids or imidacloprid.[17] A gelbait containing hydramethylnon has been effective in experiments.[19]
In the movement away from pesticides other treatments have been developed, such as the blasting of hot air into the colonies, or the application of liquid nitrogen. A microwave-emitting device can be used to "cook" the colony, or a low-current, high-voltage "gun" device can deliver an electric shock.[1]
If possible, infested wood can simply be removed from the structure and replaced, and infested trees or dead wood piles can be removed.[1]
Related Research Articles
Termites are a group of detritophagous eusocial insects which consume a wide variety of decaying plant material, generally in the form of wood, leaf litter, and soil humus. They are distinguished by their moniliform antennae and the soft-bodied and often unpigmented worker caste for which they have been commonly termed "white ants"; however, they are not ants, to which they are only distantly related. About 2,972 extant species are currently described, 2,105 of which are members of the family Termitidae.
Reticulitermes flavipes, the eastern subterranean termite, is the most common termite found in North America. These termites are the most economically important wood destroying insects in the United States and are classified as pests. They feed on cellulose material such as the structural wood in buildings, wooden fixtures, paper, books, and cotton. A mature colony can range from 20,000 workers to as high as 5 million workers and the primary queen of the colony lays 5,000 to 10,000 eggs per year to add to this total.
Mastotermes darwiniensis, common names giant northern termite and Darwin termite, is a termite species found only in northern Australia. It is the most primitive extant termite species. Contrary to common belief, this species does not form mounds as the nests are subterranean and inconspicuous. Colonies will readily occupy and infest decomposing wood but primarily live in a complex subterranean network of tunnels and galleries which they use to travel to new food sites. Colonies may eventually split and form isolated satellite colonies.
Nasutitermes corniger is a species of arboreal termite that is endemic to the neotropics. It is very closely related to Nasutitermes ephratae. The species has been studied relatively intensively, particularly on Barro Colorado Island, Panama. These studies and others have shown that the termite interacts with many different organisms including a bat that roosts in its nest and various species of ants that cohabit with the termite.
Kalotermitidae is a family of termites, commonly known as drywood termites. Kalotermitidae includes 21 genera and 419 species. The family has a cosmopolitan circumtropical distribution, and is found in functionally arid environments.
Zootermopsis angusticollis is a species of termite (Isoptera) in the family Archotermopsidae, a group known as the Pacific dampwood termites, or the rottenwood termites. As their name suggests, the dampwood termites can only survive by living off of wood that contains high amounts of moisture. They are found along the wet environments of the Pacific coast of North America. Most are found in the states of California, Oregon, Washington, Idaho, Western Nevada and in southern British Columbia. Termites are well known to be destroyers of wood, and although the dampwood termites can cause some damage, they are not as notoriously known to cause as much damage to buildings as the drywood termites. They occasionally have been carried to other parts of the country through wood shipments, but have not been able to become established in these areas due to undesirable environmental conditions.
Coptotermes gestroi, commonly known as the Asian subterranean termite is a small species of termite that lives underground. Both this species and the Formosan subterranean termite are destructive pests native to Asia, but have spread to other parts of the world including the United States. In Asia, this species is known as the Philippine milk termite.
Incisitermes is a genus of termites in the family Kalotermitidae.
Kalotermes flavicollis, the yellownecked dry-wood termite, is a species of dampwood termites belonging to the family Kalotermitidae, one of the most primitive families of termites.
The Hodotermitidae are a basal Old World family of termites known as the harvester termites. They are distinguished by the serrated inner edge of their mandibles, and their functional compound eyes which are present in all castes. They forage for grass at night and during daylight hours, and the pigmented workers are often observed outside the nest. Their range includes the deserts and savannas of Africa, the Middle East, and Southwest Asia. Their English name refers to their habit of collecting grass, which is not unique to the family however.
Cryptotermes brevis is a species of termite in the family Kalotermitidae, commonly known as the West Indian drywood termite or the powderpost termite. It is able to live completely inside timber structures or articles made of wood such as furniture without any outside source of water. It is frequently introduced into new locations inadvertently, and causes damage to the structural timbers of buildings and to wooden objects such as furniture.
Postelectrotermes militaris, the up-country tea termite, is a species of drywood termite of the genus Postelectrotermes. It is native to India and Sri Lanka. It is a serious pest of tea.
The Indo-Malaysian drywood termite,, is a species of dry wood termite of the genus Cryptotermes. It is found in Philippines, Australia, Papua New Guinea, Hawaii, and introduced to Sri Lanka. It is the smallest termite species in Australia, with 2.5 – 3.7mm in soldiers.
The domestic drywood termite,, is a species of dry wood termite of the genus Cryptotermes. It is native to Malaysia, Borneo, Australia, China and Sri Lanka. It is mainly a house termite and also found in cultivated areas. The presence of this termite can be identified by small heaps of tiny egg-like pellets of excreta. It is a larger termite species, with 3.25-5.90mm in soldiers. It is considered as a minor pest in Australia, but is a serious pest causing wood damage in other parts of the world.
The West Indian drywood termite is a species of dry wood termite of the genus Cryptotermes. It is native to Java, Indonesia and exotic to Australia, Trinidad and Tobago and Sri Lanka. It is predominantly a house termite found in natural and man-made wooden structures. Thus, this is the most commonest and most devastating drywood pest termite found in the world. It is a larger termite species, with 4.55–7.15 millimetres length in soldiers.
Marginitermes hubbardi, commonly known as the light western drywood termite, is a species of termite in the family Kalotermitidae. It is found in Central America and desert regions of southwestern North America.
Reticulitermes virginicus is a species of subterranean termite native to North America, found often in the southern United States. It was described in 1907.
Amitermes floridensis, commonly known as the Florida darkwinged subterranean termite, is a species of eusocial insect in the family Termitidae. It feeds on rotting wood, reached by a network of tunnels. It is endemic to west central Florida and was first described in 1989.
Pterotermes is a monotypic genus of termites in the family Kalotermitidae. Pterotermes occidentis is the single species in the genus. This termite lives in the extremely dry conditions found in the Sonoran Desert in southwestern United States, Baja California and Mexico. It feeds on dry wood and lives entirely within a single piece of timber.
1 2 Gold, Roger E.; Glenn, Grady J.; Howell, Harry N. Jr.; Brown, Wizzie. "Drywood Termites". AgriLife Communications and Marketing, Texas A&M University System. Retrieved 2013-11-20.
↑ Davies, Nicholas B., John R. Krebs, Stuart A. West (2012). An Introduction to Behavioural Ecology. Chichester, West Sussex: Blackwell Publishing.{{cite book}}: CS1 maint: multiple names: authors list (link)
↑ Cabrera, B.J.; M. K. Rust (July 1999). "Caste differences in feeding and trophallaxis in the western drywood termite, Incisitermes minor (Hagen) (Isoptera, Kalotermitidae)". Insectes Sociaux. 46 (3): 244–249. doi:10.1007/s000400050141.
↑ Rust, Michael K.; Donald A. Reierson (July 1977). "Using wood extracts to determine the feeding preferences of the western drywood termite, Incisitermes minor (Hagen)". Journal of Chemical Ecology. 3 (4): 391–399. Bibcode:1977JCEco...3..391R. doi:10.1007/bf00988182.
↑ Shelton, Thomas G; El al (June 2001). "Cyclic CO2 release in Cryptotermes cavifrons Banks, Incisitermes tabogae (Snyder) and I. minor (Hagen) (Isoptera: Kalotermitidae)". Comparative Biochemistry and Physiology A. 129 (2–3): 681–693. doi:10.1016/s1095-6433(01)00332-4. PMID11423337.
1 2 Lewis, V. R. Pest Notes: Drywood Termites. Publication 7440. Statewide IPM Program, Agriculture and Natural Resources, University of California. 2002.
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