The same might be true for values observed in Nearctic populations of S. (S.)rostratum(max. = 3.51%; mean = 1.45%)
and S. (N.)silvestre(max. = 3.84%; mean = 1.03%), and similar maximum values can be expected in other widespread
species of Nearctic black flies. Simulium(Nevermannia) silvestreis possibly a species complex, although cytological
and distributional data alternatively suggests that it might represent a chromosomally polymorphic species (Adler
et al. 2004). Our data on S. (N.)silvestre, although preliminary, seems to support this latter scenario. In fact, our sampled
populations from various sites in Canada and USA seem to be conspecific with populations from northern Europe
[identified as S.(N.)silvestreby P. Adler; data not shown]. Further studies will be necessary in order to establish the
specific status of allS. (N.)silvestrepopulations.