Son onbeş senede DDT nin ve diğer kuvvetli yeni sentetik ilâçların keşfi zararlı böcekler ile mücadele imkânlarını çok artırmıştır. Yukarda bahis edilen kimyevî maddelerin nisbi olarak ucuzluğu, tesirliliği ve kullanılma kolaylıkları onların zirai mahsullerin ve ormanların korunmasında kullanılmaları neticesini doğurmuş ve ayni zamanda dünyanın geniş sahalarında hastalık nakleden böceklerinde kontrolunda büyük muvaffakiyetler sağlamıştır. Bu muvaffakiyetler bu yeni insektisitlerin kullanılma imkân ve nispetlerini tespit etmek için onların geniş ölçüde laboratuvar denemelerine ihtiyacı ortaya koymuştur. 

Toxîcology is study of poisons. İt deals with the matters such as insect resistance to insecticides, relative toxicity and mode of aelion of insecticides, chemical analysis of pesticide residues and bio asssy of pesticide residue and Toxicity of insecticides. İn t his artîcfe importance of insect toxicoIogy its met h od s and apparatus have been d scusssd. At the present time insect resistance to insecticides is a weli known phsno menon. İt is a problem both in medical entomology and in agricultural entomoology. Unîil thedlscovery of DDT and other chlorinated hyd: otarfcons, this problem had not been serious, because of the very few cares repsrted. However within two years of the universal applicatlon of these insectisSck-s, it become evident that certain species had become resîstant and currently înstances of failure to achieve adequate control a re common. , . The idea of replacing the chlorinated hydrocarbons by organophosphorus compounds in order to avoid this selection of resîstant inse:* strains, has not solved the problem as some insects have become resîstant to t (i e m also. İn 1956 the concept of vigour tolerance was indroduced by Hosk'ms and Gordon. Sncreased weight or improved hiochemical condition in the insect cou!d cause «Vigour tolerance» to the insecticide rather than any specîfiç defense mechanism. Frecjuent âttempts have been made to correlate variations in rhoVphölogy and physîology with resistance and some differenceş dlstinguishing resîstant from susceptible strains have been found. These were also explained in the article. Chemical analysis of pesticide residues and bio-assay of pesticide -residues were briefly mentioned too.