Termite Food Consumption
Summary: Subterranean termite daily food consumption rates vary, among six species of termites common to the United States, from 0.015mg to 0.2mg, averaging about 0.08mg per termite per day. Formosan termite workers tend to eat slightly less than average, but make up for that with huge colonies. Termite colonies vary in size from only a small number of workers up to, perhaps, an average size of 200,000 workers in our native species, and 500,000 workers for Formosan termite colonies. Thus, an average native subterranean termite colony may eat an average of 16 grams (0.56 ounces) a day, 465 grams (1.07 lbs) a month, or 5,840 grams (12.9 pounds) in a year, while a Formosan termite colony may consume somewhat more than twice that amount. Using these numbers to figure how much cellulose in a termite interceptor, or in a wooden structure, a termite colony might eat over a period of time cannot be recommended, however, because termite colonies do not eat in one or only a few places at a time. How many feeding places the colony uses depends on the availability of different food sources, and termite interceptors--as well as structures that they are feeding in--constitute only a portion of their food supply at any given time. Scroll down to read full text of of article.
Subterranean Termites in the U.S.
The rate of food consumption varies by termite species, the kind of wood consumed, and the vigor of the termite colony. Throughout most of the United States, six species are responsible for most of the subterranean termite damage to homes and businesses, and a seventh species is poised to enter the fray in the not-too-distant future.
In the east, south, and southwest, the most common species of subterranean termite found infesting structures is Reticulitermes flavipes. Less frequently, R. hageni and R. virginicus infest structures in the same areas. In the west, from southern British Columbia to central California, the structural termite species encountered most often is R. hesperus. In the desert southwest, Heterotermes aureus is the primary subterranean termite found in structures. Food consumption, per termite, for each of these species, varies a little, with workers in the species R. flavipes and R. hesperus consuming slightly more, in general, than the others.
In some areas, notably along the coast of the Gulf of Mexico but also inland, where they have been transported in railroad ties and other materials, a sixth (imported) species, Coptotermes formosanus, better known as the Formosan subterranean termite, causes considerable damage. Formosan termite colonies tend to be larger than those of our native species, and up to 25% of their infestations in Florida are aerial, i.e., with no connection to the soil. Comparable percentages of aerial infestations should be expected in other locales having similar humidity and rainfall levels. Food consumption for this species, per termite worker, is somewhat lower than that of R. flavipes or R. hesperus, but that statistical deficit is more than compensated for by the huge colonies the species produces.
A seventh (also imported) species, Coptotermes gestroi (also known under the junior synonym Coptotermes havilandi), the Asian subterranean termite, became established in Miami, Florida, sometime after its discovery there in 1997. This termite rivals the destructive potential of C. formosanus, and we should expect it to expand its territory beyond Miami in the coming years. It is difficult to distinguish between C. formosanus and C. gestroi in the field, but the latter has been recovered, in Tennessee, from shipping crates imported from East Asia, and it is only a matter of time before the species becomes more widespread in the continental United States.
Average Rates of Food Consumption
I am indebted to Dr. Barbara Thorne for her compilation of food consumption data in the 1998 NPCA report she authored, "Biology of Subterranean Termites of the Genus Reticulitermes," (which, by the way, also included figures for Coptotermes formosanus). That compilation comprised the base data used to calculate the following figures. Any errors the reader may note in these figures are most likely mine, rather than hers.
For R. flavipes, R. hesperus and C. formosanus, the rate of food consumption varies from 0.004mg to 0.196mg, averaging--at least for R. flavipes and R. hesperus--about 0.08mg per termite per day. As mentioned earlier, C. formosanus workers eat somewhat less (ranging from 0.010mg to 0.185mg per termite per day). For this discussion, we assume that all three species are alike with regard to per-termite daily food consumption.
Termite colonies vary in size from only a small number of workers up to, perhaps, an average size of 200,000 workers in our native species, and 500,000 workers for Formosan termite colonies (these are my rough extrapolations from a covey of data reported from a variety of sources). Using these gross figures, which I hasten to add are only crude estimates, an average native subterranean termite colony may be expected to eat an average of 16 grams (0.56 ounces) a day, 465 grams (1.07 lbs) a month, or 5,840 grams (12.9 pounds) in a year, while a Formosan termite colony may eat slightly less than twice that amount.
Here, caution is in order. Statistics are crude estimates only. Attempts to extrapolate beyond these numbers to estimate how much cellulose in a termite interceptor, or in a wooden structure, a termite colony might eat over a period of time is tricky, for several very important reasons. The vigor of different termite colonies varies by a wide margin, ranging from a low of only one-fifth the average, to a high that can be two and a half times the average. Even more important is the fact that termite colonies do not eat in one place, or in only a few places, at a time. How many feeding places the colony uses depends on the availability of different food sources, and termite interceptors as well as the structures they happen to be feeding in constitute, in general, only a portion of their food supply at any given time.
When we started designing termite interceptors, we kept the above food consumption numbers in mind, but factored in one important caveat:
Termites don't feed on singular food sources in nature. Instead, they exploit a multitude of food sources at once. Individual termite workers travel a circuit, hiking from one food source to another, spending only enough time at each to ingest a small quantity of food. That food is not immediately available to produce energy, but must be broken down, in the termite's digestive system (by the termite's gut fauna), while they hike to the next food source.
It takes much more time for a termite to digest its food than to ingest it, so termites spend more time hiking than feeding. Even laboratory specimens of live termite colonies, feeding on a single food source in a soil substrate, create a labyrinth of tubes throughout the soil, and hike the tubes incessantly. This on-the-go behavior, in natural surroundings, suffices to keep the colony at the peak of health. Laboratory specimens, by comparison, are notoriously weaker and less vigorous, partly because their hiking trails, being confined to small laboratory containers, are shorter and more prone to contamination.
A practical termite interceptor will allow its store of termite food to be replenished with fresh food material after it is serviced. As long as regular inspections are conducted, none of the devices in a given installation should be allowed to run out of food before termite interdiction and inoculation work together to eliminate the termite colony.
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Links to Important Articles related to Termite food consumption:
Barbara Thorne et al discuss recent discoveries in termite biology: http://www.lfsc-courses.umd.edu/cv/docs/entm_cv/bthorne/04PCT_May03_reprint.pdf Dr. Thorne is a recognized authority in termite biology, and holds several patents on termite detection devices. She, in collaboration with James Traniello, the co-author of this article, developed the first convertible termite detector/bait station, defining the essential elements of the art. Her research led to a revolution in the field of subterranean termite detection and management.
Gunther Becker discusses termites and wood: http://www.fao.org/docrep/h2575e/h2575e01.htm
Regina Célia Gonçalves PeraltaI et al discusses wood consumption rates of forest species by subterranean termites: http://www.scielo.br/scielo.php?pid=S0100-67622004000200015&script=sci_arttext
Thomas Fuchs et al discusses food consumption of desert termites: http://insects.tamu.edu/extension/bulletins/uc/uc-016.html
Barbara Thorne et al discusses searching for and destroying subterranean termites: http://www.lfsc-courses.umd.edu/cv/docs/entm_cv/bthorne/01PCT_February04.pdf
Mary Duryea discusses termites in mulch: http://edis.ifas.ufl.edu/FR075
Jody Green et al discusses effects of moisture on termite food consumption: http://entnemdept.ufl.edu/Green_et_al_2005.pdf
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