First of all, base on the information from the food web of the project, I can tell that insect are played an important role for the food source. Most animals that present from the food web are relies on the insects for their source of food. For example, the field mouse relies on insects for food, and the fox relies on the field mouse for food, so the insect is an indirect source of food for the fox. If an insecticide is introduced into the food web, killing the entire insect population, several animals from the food web will lose their source of food. Without the insects, several animals from the food web will lose a source of food and their population will get decrease.
Secondly, insecticide create problems of their own. For example, many species of insects have become tolerant, either resistant or immune, especially to DDT, which had been the most broadly effective insecticide. Also, biologist have found that the careless or excessive uses of insecticide destroys many beneficial insects, birds, and small mammals. In addition, some insecticides, especially DDT, tend to persist in soil and water and can eventually accumulate in the body tissue of fish, wildlife, and humans. DDt also tends to combine with other chemicals in the soil, producing new toxic compounds that are more harmful than DDT alone.
In the other hand, people believed that insecticides are tremendously effective weapons in the fight against disease-carrying insects and insects that damage crops and properties. Insecticides helps control the