NOVELTY - A substituted isoxazoline compound (I) is new.    USE - The substituted isoxazoline compound is useful in agrochemicals for controlling pests, insects or mites, and for repelling ectoparasite in mammal or bird (claimed). Uses include but are not limited to Archips fuscocupreanus, Lyonetia clerkella, Phyllocnistis citrella, Acrolepiopsis suzukiella, Plutella xylostella, Cydia pomonella, Ascotis selenaria, Orgyia thyellina, Agrotis ipsilon, Helicoverpa armigera, Heliothis virescens, Manduca sexta, Scirtothrips dorsalis, Anomala cuprea, Nephotettix cincticeps, Varroa jacobsoni, Lipeurus caponis and Boophilus microplus.    ADVANTAGE - The substituted isoxazoline compound is environmental-friendly.    DETAILED DESCRIPTION - A substituted isoxazoline compound of formula (I) or its salt is new.    A1-A3=C-Y2 or N;    X1=halo, or 1-6C haloalkylthio;    X2=H, halo, cyano, nitro, 1-6C (halo)alkyl, -OR5 or -S(O)rR5;    X3=H, halo, 1-6C alkyl, 1-6C haloalkoxy or -NH2;    Y1=H, halo, or group chosen from formulae (i)-(iv), (viii) and (x);    Y2=H, halo or methyl;    R1=-C(O)R1a or -C(S)R1a;    R1a=-C(R9)(R9a)-S(O)r-R10, S(O)t(R10)=NR11 or group chosen from formulae (xv-xx);    R2=H, cyano, 1-6C alkyl in which 1-4C alkyl is optionally substituted by R13 or 1-6C alkoxy;    R3=1-6C haloalkyl or 3-8C halocycloalkyl;    R4=H, cyano, phenyl or aromatic heterocyclic group of formula (vi) or (vii);    R9=H, halo or 1-6C alkylsulfonyl;    R9a=H, halo or 1-6C alkyl;    R10=cyano, 1-6C alkyl, 1-4C alkyl optionally substituted by R14, -C(O)R15, -C(O)OR16, -C(O)N(R17)R16, group chosen from formula (xxi)-(xxvi), phenyl or group chosen from formulae (vi), (vii), (ix), (xi) and (xii)-(xiv);    R11=H, cyano, nitro, 1-6C (halo)alkyl, -C(O)R15, -C(O)OR16 or 1-6C (halo)alkylsulfonyl;    R12=fluoro, nitro, -OH or 1-4C (halo)alkyl;    R13=halo, cyano, 3-6C cycloalkyl, -OR20, -S(O)rR21, -N(R23)R22, -C(O)R24, -C(O)OR25, -C(S)N(R26)R25, phenyl or group chosen from 14 groups e.g. groups of formulae (i)-(v);    R14=halo, cyano, -C(O)R24, -C(O)OR25, phenyl or group of formula (xi);    R15=1-6C (halo)alkyl, 3-6C cycloalkyl, phenyl optionally substituted by (Z)p1 or group of formula (i), (ii), (iv), (v), (vii), (viii), (x) or (xi);    Z=e.g. halo;    R16=1-6C (halo)alkyl, 3-6C cycloalkyl, 2-6C alkenyl or 2-6C alkynyl;    R17=H or 1-6C alkyl;    R18=H or 1-4C (halo)alkyl;    R19=fluoro or 1-4C (halo)alkyl;    R20=1-4C (halo)alkyl, -C(O)R27 or -C(O)OR28;    R21,R24,R28=1-4C (halo)alkyl;    R22=1-4C alkyl, -C(O)R27 or -C(O)OR28;    R23=H or 1-4C alkyl;    R25=1-4C (halo)alkyl or 3-6C cycloalkyl;    R26=H or 1-4C alkyl;    R27=1-4C (halo)alkyl, 3-6C cycloalkyl, phenyl optionally substituted by (Z)p1, group of formula (i), (ii), (v), (vii) or (xi);    p1=1-3;    p2,q4,q5,r=0-2;    p3,p4,t=0 or 1;    q1=0-7;    q2=0-9;and    q3=0-5.    "Full definitions are given in the Definitions (Full Definitions) Section."