Hilltopping Insects

[Kenelm Philip]

> Since Insects can not see far I doubt that the hill means much to them.

Compound eyes lack the ability to focus, so the acuity of insect vision is
measured simply as _angular_ resolution, independent of distance. See
Wigglesworth's book for the retinal image of a distant church steeple
formed by a compound eye.

> However hills generate air currents and offer gradients of habitats as
> the[y?] get higher and higher.

That might help once an insect gets close to a hill--but the _claimed_
advantage of hilltopping is that a single isolated hill will attract
insects from a wide surrounding area.

I have also seen Tabanids hilltopping in the Canadian Arctic Archipelago
on tiny gravel hills only 4 to 6 feet high. Not much habitat gradient
there...  

One could make an argument involving air currents to explain the behavior
of some _Oeneis_ species on windy days: when disturbed they take off
downwind--and then slowly fly back to the ridgetop against the wind, and
sit on the sheltered side of the  ridge. However, the same _Oeneis_ are
also on the ridge on calm days...

							Ken Philip
fnkwp at uaf.edu