Sixteen isoenzyme patterns were analyzed for five Colombian Lutzomyia species. The average unbiased expected heterozygosity levels ranged from 0.098 (Lu. youngi) to 0.215 (Lu. torrvida). The five species samples, taken all the isoenzymes employed, were significantly deviated from the Hardy-Weinberg equilibrium by homozygous excess with classical as well as Markov chain exact tests. Possible causes:(1) Wahlund effect within populations due to subdivision and/or sampling. Endogamy could be discarded because