Pyridinium salt and pest control agent

A compound represented by formula (I-a) or formula (II-a):

• wherein:
• X1 represents a halogeno group, a halogeno group-substituted or unsubstituted C1-6 alkyl group, or a halageno group-substituted or unsubstituted C1-6 alkoxy group;
• m represents the number of X1 and is any integer of 0 to 5;
• any two of X1 may be bound together to form a bivalent hydrocarbon group;
• Y represents a single bond or a substituted or unsubstituted C2-6 alkenylene group, wherein the substituent on the C2-6 alkenylene group represented by Y is a halogeno group, a halogeno group-substituted or unsubstituted C1-6 alkyl group, a halogeno group-substituted or unsubstituted C1-6 alkoxy group, a C1-6 alkylthio group, a C1-6 alkylsulfinyl group, or a C1-6 alkyl sulfonyl group;
• X2 represents a halogeno group, a halogeno group-substituted or unsubstituted C1-6 alkyl group, a halogeno-substituted or unsubstituted C1-6 alkoxy group, or a nitro group;
• n represents the number of X2 and is any integer of 0 to 2;
• Q2 represents a substituted or unsubstituted C6-10 aryl group or a substituted or unsubstituted 5- to 6-membered heteroaryl group, wherein the substituent on the C6-10 aryl group or 5- to 6-membered heteroaryl group represented by Q2 is a halogeno group, a halogeno group-substituted or unsubstituted C1-6 alkyl group, a halogeno group-substituted or unsubstituted C2-6 alkynyl group, a hydroxyl group, a halogeno group-substituted or unsubstituted C1-6 alkoxy group, a substituted or unsubstituted benzyl group, a halogeno group-substituted or unsubstituted C1-6 alkoxycarbonyl group, a halogeno group-substituted or unsubstituted C1-6 alkylthio group, a halogeno group-substituted or unsubstituted C1-6 alkylsulfonyl group, a halogeno group-substituted or unsubstituted C1-6 alkylsulfonyloxy group, a di C1-6 alkylamino group, a halogeno group-substituted or unsubstituted C3-8 cycloalkyl group, a halogeno group-substituted or unsubstituted C3-8 cycloalkyloxy group, a substituted or unsubstituted phenyl group, a pentafluorosulfanyl group, or a cyano group;
• Zq− represents a counter ion;
• q represents a valence of the counter ion and is 1 or 2;
• and
• “substituted” means that any hydrogen atom of the group which is to become the mother nucleus is substituted with a C1-6 alkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group, a C3-8 cycloalkyl group, a C6-10 aryl group, a C6-10 aryl C1-6 alkyl group, a 3- to 6-membered heterocyclyl group, a 3- to 6-membered heterocyclyl C1-6 alkyl group, a hydroxyl group, a C1-6 alkoxy group, a C2-6 alkenyloxy group, a C2-6 alkynyloxy group, a C6-10 aryloxy group, a C6-10 aryl C1-6 alkoxy group, a 5- to 6-membered heteroaryloxy group, a 5- to 6-membered heteroaryl C1-6 alkyloxy group, a formyl group, a C1-6 alkylcarbonyl group, a formyloxy group, a C1-6 alkylcarbonyloxy group, a C6-10 arylcarbonyl group, a C1-6 alkoxycarbonyl, a C1-6 alkoxycarbonyloxy group, a carboxyl group, a halogeno group, a C1-6 haloalkyl group, a C2-6 haloalkenyl group, a C2-6 haloalkynyl group, a C1-6 haloalkoxy group, a C2-6 haloalkenyloxy group, a C1-6 haloalkylcarbonyl group, an amino group, a C1-6 alkyl-substituted amino group, a C6-10 arylamino group, a C6-10 aryl C1-6 alkylamino group, a formylamino group, a C1-6 alkylcarbonylamino group, a C1-6 alkoxycarbonylamino group, an aminocarbonyl group, a dimethylaminocarbonyl group, a phenylaminocarbonyl group, an N-phenyl-N-methylaminocarbonyl group, an imino C1-6 alkyl group, an N-hydroxy-iminomethyl group, a (1-(N-hydroxy)-imino)ethyl group, a (1-(N-hydroxy)-imino)propyl group, an N-methoxy-iminomethyl group, a (1-(N-methoxy)-imino)ethyl group, an aminocarbonyloxy group, a C1-6 alkyl-substituted aminocarbonyloxy group, a mercapto group, a C1-6 alkylthio group, a C1-6 haloalkylthio group, a C6-10 arylthio group, a 5- to 6-membered heteroarylthio group, a C1-6 alkylsulfinyl group, a C1-6 haloalkylsulfinyl group, a C6-10 arylsulfinyl group, a 5- to 6-membered heteroarylsulfinyl group, a C1-6 alkylsulfonyl group, a C1-6 haloalkylsulfonyl group, a C6-10 arylsulfonyl group, a 5- to 6-membered heteroarylsulfonyl group, a C1-6 alkylsulfonyloxy group, a C1-6 haloalkylsulfonyloxy group, a tri C1-6 alkyl-substituted silyl group, a tri C6-10 aryl-substituted silyl group, a pentafluorosulfanyl group, a cyano group, or a nitro group.