It is shown that the frequency of exoskeleton anomalies authentically is higher among female taiga ticks (Ixodes persulcatus) from populations of the suburbs of Bratsk in comparison with the individuals from the vicinities of Irkutsk. This pattern has been traced on tick samples for two years and also implies formation of both single and double anomalies for all the revealed types of exoskeleton anomalies. The reasons of such distinctions are discussed, as well as probable connection of this phenomenon to the morbidity rate of the population in the north and south of the Irkutsk region caused by tick-borne infections.