Introduction to termites
Termites are a group of insects that are classified as the infraorder Isoptera. While termites are commonly known as “white ants’, they are not closely related to ants.
Figure 1: Worker(left) and Soldier(right) Photo from: http://blog.sina.com.cn/s/blog_12f59f1cb0101eahd.html
Trophallaxis is one of the remarkable characteristics of termites. It is the transfer of food or other fluids among members of a community through mouth-to-mouth feeding.
Termites are eusocial insects, and they live in colonies and communicate with signals. They divide labors among castes: reproductives, workers and Soldiers are three main roles of termite’s social organization.
In a mature termite colony, the reproductive, babies and soldiers cannot take food independently. Thus, workers have to feed them mouth to mouth and let the food be digested by babies, soldiers and queen.
Life cycle: The life cycle of a termite begins with an egg going through a developmental process called incomplete metamorphosis. Different caste termites have different life cycles. During March, alates fly away from the nest and mate in a proper place which later becomes a nest. The queen can live up to tens of years, while the average life span of workers is 2 to 3 years.
Figure 2: Basic Life Cycle of Termites Photo from: ‘Termite Management For Homeowners’ Arizona University
Distribution of termites
Termite is an ancient social insect in the world for about 0.13 billion years. They are now filling nearly every corner of the globe, from tropical regions to subtropical ones, which occupies 50% of the earth's area.
Figure 3: The orange part shows world distribution of termites Photo from: ‘Termites in Zhejiang’ （2015）Zhejiang Education Press
Accounting for the effect of warm wet air current from the Pacific and Indian Oceans, many provinces with warm climate, plentiful water and abundant vegetation own special preferences for termites.
Figure 4: The orange part shows China distribution of termites Photo from: ‘Termites in Zhejiang’ （2015）Zhejiang Education Press
Zhejiang Province Distribution
According to the results above, Zhejiang is one of the regions mostly occupied and plagued by termites.
Termites feed on woods, and digest lignocellulose. When they feed on housing construction, landscaping and other commercial products, they become economic pests.
The harm that termites bring to human mainly reflects in two aspects.
1. Eating lignocellulose materials as food. Termites take materials rich in lignocellulose as food, which causes property damage to human beings. It is reported that, the direct loss induced by termites is beyond 220 billion dollars per year.
2. Leaving holes in the structure while perforating. The holes affect the integrity and security of buildings, dams and trees. What's more, the hazards caused by termites to communal facilities such as large reinforced concrete bridges, gas lines, are frequently reported these years. It really influences public safety and people's life in a negative way.
The characteristics of the termite invasion
Termites are photophobic so it often takes a long time to discover termite invasion. However, once being discovered, they usually have caused a certain financial loss or major accidents. This habit also makes termites one of the most destructive city pests.
First, termites have the strong adaptability and viability. As long as there are proper temperature, humidity and nutrient, termites can survive.
Second, their reproductive capacity is severely high. In the breeding heyday, a mature termite queen’s daily oviposition is over ten thousand. The spawning of one year reaches up to five hundred millions.
Third, termites could achieve different-distance spread and distribution by virtue of flight spread, pervasive invasion and factitious carry, owning to their strong transmission capacity.
Fourth, the transcaton of wood helps termites spread. Taking the Coptotermes formosanus as an example, which is the most harmful termite around the world; however this species once only distributed in several regions, such as Chinese mainland and Taiwan. With the transportation of massive supplies in World War II, these termites’ distribution range has gradually enlarged. At present this kind of termites has caused serious damages in numerous countries and regions, turning into cosmopolitan pest. According to incomplete statistics, all over the world, the annual expenditure of termites control exceeds a billion dollars.
Owing to their wood-eating habits, many termite species can do great damage to unprotected buildings and other wooden structures. Their habit of remaining concealed often results in their presence being undetected until the timbers are severely damaged and exhibit surface changes. Once termites have entered a building, they do not limit themselves to wood; they also damage paper, cloth, carpets, and other cellulosic materials. In April 2011, wood-eating termites were blamed for reportedly consuming more than $220,000 worth of Indian rupee notes.
Nowadays, people control termites in two main ways—chemical pesticides and baiting systems. Both of the methods have merits and shortcomings.
For decades, humans have produced a variety of chemicals to control termites. These chemical pesticides assist humans to kill a large number of the annoying insects. In recent years, however, the health and environment concerns caused by the chemicals become a heated topic. We list some of the widely used chemical termicides, and make a comparison among them:
Comparisons Among Different Termite Testicides
By comparison, avermectins seem to be safer and eco-friendlier. They exert limited negative influence on people and pets and if the chemical placement location is away from the water, it will not harm to environment.
The baiting system employs a totally different approach. The baits consist of some ‘tasty’ food which attract termites, combined with some slow-acting substance lethal to termites. Foraging termites consume the bait and share it with their nestmates, resulting in a gradual decline in termite numbers.
All of the baiting systems possess three main steps:
Step 1: Monitoring
Termites are detected by installing plastic monitoring stations around the perimeter of the buiding.
The device is a plastic cylinder, with slits along the sides of it for termite entry. Each device is provisioned with some wood to attract termites.
Step 2: Bait Delivery
When termites are found in a monitoring station, the untreated wood is replaced with the bait combined with a slow-acting termite inhibitor.
Step 3: Continued Monitoring
When the termites are no longer found, the baits are replaced by untreated wood to continue to monitor
All in all, Baiting systems are eco-friendly, but it takes a long time to kill a nest.
Either chemical pesticides or baiting systems has its advantages and disadvantages. It is hard to determine which is better.