We studied, simultaneously, postnatal variation in ectoparasite load in neonates, lactating, pregnant and non-pregnant females — in a free-ranging nursing colony of Geoffroy's bat (Myotis emarginatus) in Kerend Cave, western Iran. During this survey we monitored 120 (78 ♂♂, 42 ♀♀) neonate bats, as well as 21 pregnant, 42 lactating and 15 non-pregnant females. These individuals yielded a total of 1857 wing mites of the species Spinturnix emarginata. The first 14 days following the birth of pups was found to be associated with a rapid increase in numbers of S. emarginata on the neonates — up to an average (± SE) 21.3 ± 5.34 ectoparasites per individual. This was followed by a sudden reduction in parasite load to a stabilised rate of 5.9 ± 0.98 parasites per individual at the end of the postnatal period. The average ectoparasite load for all neonates over 42 days of the postnatal period was 11.5 ± 0.81. No significant difference was noted as regards average parasite load for neonate males (11.9 ± 1.11) and females (10.8 ± 1.06). In contrast, the average parasite load for lactating females (at 8.6 ± 0.93) was significantly higher than the corresponding figure for pregnant females (4.1 ± 0.39). The average parasite loads for lactating females and neonates do not differ significantly. Where reference was made to the ratio of body mass to length of forearm, no significant correlation was found between parasite load and body condition among either male or female neonates, or pregnant, lactating and non-pregnant females. The study therefore confirms that host-parasite interactions between the bat M. emarginatus and the wing mite S. emarginata is tuned proximally in such a way that bat hosts at any stages of their life cycle (male and female pups, pregnant, lactating, and non-productive females and adult males) resist parasites without paying the costs of parasitism in terms of reduced body mass or length adjusted body mass (W/FA).