Compounds of the formula:
and their alkali metal or non-toxic acid addition salts, wherein:

(a) R' is hydrogen or lower alkyl; and R 2 is lower alkyl lower alkoxy, 2,2,2-trifluoroethyl, hydroxy-lower alkyl, 2-methoxyethoxymethyl, lower alkoxycarbonyl-lower alkyl, lower alkanoyloxy-lower alkyl, aryl-lower alkyl, aryloxy-lower alkyl, thiocyanatoacetyl, lower cycloalkyl-lower alkyl, lower cycloalkyl, lower cycloalkenyl, lower alkenyl, allenyl, lower alkynyl, C 2 -C 16 alkanoyl, halo-lower alkanoyl, aryl-lower alkanoyl, N,N-di(lower alkyl)sulfamoyl, 1,2,3,4-tetrahydronaphthyl, arylthio, aryl or aroyl; or R' and R 2 together with the nitrogen atom to which they are attached form a saturated 5- or 6- membered heterocyclic group optionally containing a further heteroatom selected from 0, S and N, said N atom bearing a hydrogen atom or a lower alkyl or aryl group, said heterocyclic group optionally being substituted on a carbon atom by 1 or 2 lower alkyl groups;
(b) X is 0, S, SO or S0 2 ;
(c) Y is halogen, lower alkyl, tri(lower alkyl)silyl, lower alkoxy, or a group of the formula R 3 S- or R 3 S0 2 - wherein R 3 is lower alkyl or aryl; n is 0 or 1; and
(d) R is lower alkyl, lower alkenyl, lower cycloalkyl, allenyl, lower alkoxy-lower alkyl, aryl-lower alkyl, aryl, heteroaryl or heteroaryl-phenyl, with the proviso that when X is SO 2 , R can also be-NR 1 R 2 wherein R' and R 2 are as defined above;

the term "lower" as applied to an alkyl, alkoxy, alkanoyl, alkenyl or alkynyl group means that said group has up to 6 carbon atoms; "lower" as applied to a cycloalkyl group means that said group has from 3 to 7 carbon atoms; "lower" as applied to a cycloalkenyl group means that said group has from 4 to 7 carbon atoms;
and the term "aryl" means unsubstituted phenyl, unsubstituted naphthyl or substituted phenyl.
The compounds are insecticidal, particularly larvicidal agents, and some have acaricidal and miticidal activity. They are particularly used as blowfly larvicides on sheep and cattle.