Diurnal activity of Ixodes ricinus in Denmark: Aspects of physiological age and genotypic variation

Four different alleles in the nymphal Ixodes ricinus were found for the Mal ate Dehydrogenase enzyme (MDH). The allele Frequency of the MDH genotypes i n nymphal I. ricinus was observed to change during the day. Some genotypes were present in the morning, but not in the afternoon and evening. The phys iological age of the nymphs was also determined. No significant correlation could be found between physiological age and genotypes. Based on the resul ts it must be anticipated that the comparability of tick samples not. only differs in quantity but also in quality for various hours, but not necessar ily for various months. Therefore isoenzyme analysis of nymphs at least as regards the MDH alleles appears to be a convenient biological tool to analy se differences in host seeking behaviour.