the present invention relates to synergistic arthropodicidal composition of several pyrethroidal active ingredients causing no damage to warm - blooded organisms comprising pyrethroides and piperonyl butoxide as active ingredient which comprises as pyrethroidal active ingredient 0 . 1 - 20 % by weight of 1stransr - alpha - cyano - 3 - phenoxy - benzyl - 3 - - 2 , 2 - dimethyl / cyclopropane - cyrboxylate of the formula i ## str1 ## 0 . 05 - 10 % by weight of cis - trans - tetramethrin - cis - trans - chrysantemate ) or trans - tetramethrin of the formula ii ## str2 ## and a further pyrethroide , 0 . 1 - 40 % by weight of piperonyl butoxide of the formula iii ## str3 ##