Female house flies were treated topically with p32 labeled methyl 
parathion. A total of nine metabolites were observed on thin-layer plates. 
In addition to an unidentified compound, orthophosphate, monomethyl and 
dimethyl phosphate, methyl paraoxon, phosphorothioate, dimethylphosphoro- 
thioate, desmethyl analog of methyl parathion and methyl paraoxon were 
observed (683). 
A fine discussion of the influence of esterases in insects on the 
degradation of organophosphates of the E-605 series can also be found in 
Pflanzschutz-Nachrichten 19, 1-34 (1966). 
When p?2..1abeled methyl parathion was applied to cotton leaves, 
analyses indicated a half-life of 24 hours. Four compounds containing 
p32 were found in the residue. Two were identified as methyl parathion 
and methyl paraoxon and two were unidentified. Under conditions of high 
temperatures more of the methyl parathion in the cotton leaf was converted 
to methyl paraoxon. Other studies with plants have shown the presence of 
phosphoric, dialkyl thiophosphoric, dealkyl thiophosphoric and dealkyl 
phosphoric acid (342). When applied to rice plants, methyl parathion gave 
rise to methyl paraoxon and to desmethyl methyl parathion (1021, 1022). 
Paraoxon was detected, in samples of field-sprayed lettuce, four hours 
after application of parathion. Two other carboxyesterase inhibiting com- 
pounds, believed to be the S-ethyl and S-phenyl isomers of parathion, were 
also observed (290). In parathion-treated bean plants (Phaseolus vulgaris), 
paraoxon, p-nitrophenol, and possibly S-ethyl parathion were observed (402). 
When roots of wheat plants were treated with parathion solutions, the 
leaf guttation fluid contained an active anticholinesterase which was shown 
to be paraoxon (342). 
In the course of attempts to control Culex pipiens s.l., it was found 
that Bacillus subtilis was very effective in inactivation of parathion and 
methylparathion. A metabolite was identified as the amino analog of the 
original material (1529). Under culture conditions, B. subtilis metabolized 
methyl- and ethyl-parathion to their respective amino analogs. In additional 
studies with methylparathion, both desmethyl parathion and desmethyl-amino- 
methylparathion were observed. No oxon analog was detected (1018). In other 
studies, parathion was hydrolyzed by microorganisms to p-nitrophenol (626). 
Soil bacteria decomposed parathion but metabolites were not isolated 
(1074). In soils of low numbers of microorganism (autoclaved soil) or of 
low microorganism activity (dry soils), parathion persisted for a relatively 
long time. No aminoparathion was found in autoclaved soils. Yeast reduced 
parathion in soil to aminoparathion (871). 
268 
