Entry via the Mouth

Insecticides used in earlier days were referred to as stomach poisons, and for many years this was a major group of insecticides. Examples of such insecticides are various arsenicals 

As for contact insecticides, dichlorvos and nicotine were found to enter the insects through the cuticle despite their high vapor pressures (dichlorvos, 0.012 mm Hg [at 20°C] and nicotine, 0.0425 mm Hg [at 25°C]) (Gallery, 1967). Matsumura (1959) studied the uptake of malathion by American cockroaches from a glass surface and found that the highest amount was picked up by the legs, whereas the trachea played a very minor role in the total pickup procedure. The vapor pressure of malathion is 4 x 10-5 mm Hg at 30°C. 

and Gardiner, B.G., Penetration of malathion into locusts, Pestic. Sci., 1,217,1970. Benezet, H.J. and Forgash, A.J., Penetration and distribution of topically applied malathion in the house fly, /. Econ. EntomoL, 65, 53,1972. 

The effect of methyl bromide on the respiration of the cadelle Tenebroides manritanicus (L.), Can. ]. ZooL, 34, 405,1956. 

The action of fumigants on insects. II. The effect of hydrogen cyanide on the activity and respiration of certain insects, Can. ]. Zool., 39,437,1961. 

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