Halogen-substituted quinoline derivatives and ectoparasite control agent

A compound represented by formula (I) or a salt thereof:

• wherein
• R1 represents alkyl having 1 to 6 carbon atoms optionally substituted by a halogen atom or cyano;
• alkenyl having 2 to 6 carbon atoms optionally substituted by a halogen atom or cyano;
• alkynyl having 2 to 6 carbon atoms optionally substituted by a halogen atom or cyano;
• group —O—R5 wherein R5 represents alkyl having 1 to 6 carbon atoms optionally substituted by a halogen atom or cyano, alkenyl having 2 to 6 carbon atoms optionally substituted by a halogen atom or cyano, or alkynyl having 2 to 6 carbon atoms optionally substituted by a halogen atom or cyano;
• or group —S—R5 wherein R5 is as defined above,
• R2 represents alkyl having 1 to 4 carbon atoms optionally substituted by a halogen atom,
• any one of R3 and R4 represents a hydrogen atom and the other represents a fluorine atom, a chlorine atom, a bromine atom, or —CF3, and
• X represents a fluorine atom or a chlorine atom.