chemical preparation of the products of the invention a person skilled in the art is regarded as having at his disposal inter alia the entire contents of u201c chemical abstracts u201d and of the documents which are cited therein as discussed above amitraz is well known in the art and can be obtained from commercial source igr compounds are another class of insecticides or acaricides which are provided for in the bait formulations in this invention compounds belonging to this group are well known to the practitioner and represent a wide range of different chemical classes these compounds all act by interfering with the development or growth of the insect pests compounds with an ovicidal and or larvicidal effect on the immature stages of various ectoparasites are already known for example from u s pat no 5 439 924 among these compounds described are those igr compounds which act either by blocking the development of the immature stages eggs and larvae into adult stages or by inhibiting the synthesis of chitin insect growth regulators are described for example in u s pat nos 3 748 356 3 818 047 4 225 598 4 798 837 and 4 751 225 as well as in ep 179 022 or u k 2 140 010 french patent no a 2 713.