The insecticidal, anticholinesterase, and hydrolytic properties of a series of phosphoramidothiolates were examined with emphasis on structure-activity relationships. These compounds are surprisingly toxic to houseflies although they are not unusually strong inhibitors of cholinesterase. However, in-hibited cholinesterase does not spontaneously recover

Samples of fat, muscle, liver, lung, blood, and bile from a steer which received a single dose of [5-14C]methoprene were analyzed for radioactive residues. No primary methoprene metabolites could be characterized, but the majority (16-88%, depending on tissue) of the total tissue radioactiv-ity was positively identified as [14C] cholesterol. A total of 72% of the bile radioactivity was contributed by cholesterol, cholic acid, and deoxycholic acid. Radioactivity from catabolized methoprene was also associated with protein and cholesteryl esters of fatty acids.Methoprene (1, isopropyl (2E,4E)-ll-methoxy-3,7,lltrimethyl-2,4-dodecadienoate, ZR-515, trademark Altosid) is the most commercially advanced example of a class of insect growth regulators (IGR's) with juvenile hormone activ-