**Author details**

Dhiraj Saha\*

Insecticide resistance is the result of an increase in the ability of individuals of an insect species to survive insecticide application and is an important example of man-driven evolution [225]. Alleles conferring resistance may arise and spread in populations and to other populations with variable success, depending on factors such as selective forces, genetic variability, gene flow, population size and environmental conditions [220]. Studies that map the population structure of pest insects, as well as the potential for gene flow between populations, are needed to understand the development of resistance and prevention of its spread [226, 227]. Devel‐ opment of resistance is often rapid in isolated populations that have been treated by insecti‐ cides [228]. The rate of development of insecticide resistance may, however, be influenced by gene flow between treated and untreated populations by maintaining the frequency of resistance alleles at a low level [229]. Contaminant exposure was a poor predictor of population structure and the level of gene flow was a better predictor of relatedness [230]. Gene flow may balance divergence by opposing the effect of selection pressures [229]. Population genetic patterns should therefore be investigated with reference to geographical variability, as well as selection pressure. Detoxification resistance occurs when enhanced levels or modified activities of biotransformation enzymes prevent the insecticide from acting on its site of action because the metabolites produced have little or no activity compared with the original substance [231]. These changes may be due to mutations resulting in a protein with slightly

As chemical control is frequently used to avoid economic damage, the sucking insects have been subjected to major selection pressure. Insecticides will probably continue to be the main control method in the near future and therefore it is important to study the structure of sucking insect population and change in insecticide susceptibility. There are several techniques for estimating the genetic diversity such as randomly amplified polymorphic DNA analysis, microsatellites, minisatellites, restriction fragment length polymorphism analysis and ampli‐ fied fragment length polymorphism (AFLP) analysis. DNA markers are also suitable for use with small amounts of insect material and can be used with stored, dry or old samples. Some have complex multi-locus banding patterns, which may be of a non-Mendelian nature (e.g. randomly amplified polymorphic DNAs (RAPDs)). They have an expanding range of appli‐

The author expresses his sincere thanks to the Head, Department of Zoology, University of North Bengal, for providing laboratory space. The author also expresses sincere appreciation to those scientists and authors based on whose concept, hypothesis and work this chapter has been developed. The author also expresses his thanks to the University of North Bengal for providing uninterrupted local area network that has immensely helped in searching and collecting information. The author also expresses his sincere thanks to InTech Open Access Publishing Group, editor of the book '*Insecticide Resistance*' Prof. Stanislav Trdan (University of Ljubljana, Biotechnical Faculty, Dept. of Agronomy, Chair for Phytomedicine, Agricultural

different properties or altered expression.

370 Insecticides Resistance

**Acknowledgements**

cations, many involving intra- and interspecific discriminations.

Address all correspondence to: dhirajsaha\_nbu@rediffmail.com; dhirajento.nbu@gmail.com

Insect Biochemistry and Molecular Biology Laboratory, Department of Zoology, University of North Bengal, Raja Rammohunpur, P.O.- North Bengal University, Siliguri, District - Darjeeling, West Bengal, India
