unidentified (Hymenoptera: ?), Torsby, Sweden. This insect (about 5 mm long) was
seen crawling along the ground.
It has vestigial (reduced and non-functional) wings which indicate
that individuals of this species are well adapted to living on the ground.
A reduction in wing size was aparently selected during evolution because
larger winged individuals could not find food as efficiently as smaller winged ones due to
obstacles entangling wings. Possibly the wing size was reduce by means of "genetic drift"
whereby there is no selection pressure for flight and thus over many thousands of years the gene(s)
for larger wings are lost by random means in a small population that then spreads again over a larger area.
If there is a large population, then genetic drift could not explain the reduction of wing size
since the gene for wings would always be present in about the original proportion (i.e. 100%).
It is interesting that some
species of hymenoptera have lost their wings during evolution while others do not even though they all appear to live primarily on the ground. Worker ants
forage entirely on the ground and so none have wings. The ant kings and queens of all or most species have wings which are used to fly up high in the sky where they mate
with less-related individuals from other nests some tens to hundreds of meters away from their own nest.
Images © 2000 by John A. Byers, Chemical Ecology.