Roads and Leps (was medflies in Tampa)

[Mark Walker]

John Calhoun wrote:

> Mark Walker wrote:
> 
> > All of this in addition to added pollutants and the replacement of
endemic
> > plants with "artificial" roadside flora.
> > 
> > I wonder how much of an impact this has had on butterfly populations
over
> > the last 3 
> 
> 
> One species that has definately benefited from "artificial" roadside 
> plantings is the wild indigo dusky wing, Erynnis baptisiae, a skipper of 
> eastern North America. ... <SNIP>

> A second example is the spread of the silvery blue, Glaucophyche 
> lygdamus couperi, as a result of the widespread planting of exotic 
> tufted vetch, Vicia cracca, along weedy roadbanks in New York (see Dirig 
> and Cryan, 1991, J. Lepid. Soc, 45:272-290.
> 
> Finally, the rapid southward spread of the meadow fritillary, Boloria 
> bellona, has been attributed to adults using highway rights-of-way as 
> dispersal corridors.
> 
> Although the destruction of native habitats is largely detrimental, some 
> species have used it to their advantage and continue to expand their 
> ranges as a result.

John,

Thanks for the very interesting info.  I, myself have done an extensive
amount of collecting along roadsides - so they provide easy access for me
as well (guess that's another reason not to complain too much).  Many of
the butterflies seen on roadsides would be totally inaccessible otherwise,
as anyone who's lost sight of one over and above the canopy can attest to.

Interesting about E. baptisiae, a species I've just recently added to my
collection having spent my first spring Down East.  I caught it on Wild
Indigo, but find it interesting that it has adapted to crownvetch.  Some
species, especially the duskywings, seem to adapt well to roadside living. 
They are either good at dodging (which I doubt) or are just so prolific
that they beat the odds of being decimated by cars.  I recall a species I
"ran" into on a dirt road in Ocala National Forest, Florida, by the
thousands (hundreds of thousands, I suspect).  Even driving slowly, many
would not move out of the way (this is only interesting info, not really
pertinent to the point I'm making, because this road was far from being
busy).

As for Blues, though, I've only seen an abundance of roadside Blues where
the roads are small and little traveled.  Since the species are so local,
they do survive on habitats sufficiently displaced from traffic and can
therefore be commonly found near even busy roadsides.  I find it difficult
to believe that populations are thriving in and only on the introduced
flora of busy roadside habitats, unless these habitats extend well beyond
the roadside.  I'll have to read the journal paper you've referenced.  I
have seen many G. lygdamus here in West Central Vermont along roadsides, a
species which I believe was less common a half century ago.

In Southern California, where fields and undeveloped lands are getting
scarcer and scarcer, the roadside butterfly fauna has definitely declined
over the past 30 years.  The weeds may remain, but the numbers and
diversity of the butterflies have decreased.  The missing population of
Anthocharis pima in the Jurupa Hills can probably be attributed (at least
to some extent) to the introduced traffic from Interstate 10, Route 60,
Interstate 15, and the encroaching housing developments.  There's plenty(?)
of remaining habitat in the hills, but the Orange Tips are gone.

Your point about the use of roads for dispersal corridors is well made. 
Here in Vermont, where the woods are quite thick in the summer, the roads
provide access to nectaring sources and allow for easy movement between
meadows and fields.

So roads are not all bad for all butterflies.  And they can be good for
butterfly enthusiasts.  Still, for some species (especially those which
colonize locally), highways and byways seem to be more of a detriment.

Mark Walker
Castleton, VT.