[ncsc-moths] Moths, Maples, and Weather--some ecological observations
- From: "J. Merrill Lynch" <jmerrilllynch@xxxxxxxxx>
- To: ncsc-moths@xxxxxxxxxxxxx, tn-moths <tn-moths@xxxxxxxxxxxxx>, carolinaleps@xxxxxxxx
- Date: Thu, 24 Feb 2011 17:29:21 -0500
I've been wondering about the relationship between the emergence of certain
moths, the beginning of the maple sap flows, and the influence of
weather here in the northern mountains. This year the first moths appeared
on Feb 14th; since then I've had moths flying almost every night. I've had
up to eleven species--almost exclusively at my sugar bait--collectively
known as pinions and sallows, and all members of three closely related
genera: Lithophane, Eupsilia, and Pyreferra. One of the correlations seems
to be closely tied to temperature: on those nights where the
temperature has been in the low to mid 40's or above at sunset, I've seen
moths. The two best nights for # of species and individuals occurred
Feb. 18 and 21 when temps were 50+ at sunset.
In a typical winter there are usually occasional mild spells when moths are
active. This did not happen here this winter. I went back and checked the
weather data from the nearest NWS weather station located in Boone which is
about 15 miles away but at about the same elevation. Since late November,
the average daily temperature has been in the 20's and 30's with few
exceptions. Starting around Feb. 13th average daily temps increased to the
40's with high temps getting into the low 60's on a couple of days. This
warm-up correlates with the breakdown of a persistent negative Northern
Arctic Oscillation (NAO) which has been present all winter and has been
responsible for much colder than average temps across much of eastern North
America (and near record snows in Great Britain!). For an explanation of
this meterological phenomenon go to this link:
http://www.ldeo.columbia.edu/res/pi/NAO/ . [As a side note, for those
birders among you, there is an interesting discussion in the latest Winging
It about the relationship between the NAO and wintering Dovekie distribution
in the northern Atlantic].
The other interesting correlation is that moth emergence also seems to be
tied to the beginning of the sugar maple sap flows. I tap maples on my land
every year to make syrup so I'm keenly aware of when the sap starts
flowing. Maple sap flow is highly correlated with temperature and
atmospheric pressure. Flows usually start (where I live--anywhere from late
January to early March depending on the year) on sunny, high-pressure
days when daily highs get into the 50's or above but dip to freezing or
below at night. This year the first major flow started the week of Feb 13th
almost to the day when I started seeing moths and also coinciding with the
first warm-up of the year! This makes a lot of sense when you think about
it: all of the moths coming to the sugar bait overwinter as adults and have
functional mouthparts that they use to sip liquids. I have had many of
these same moths come to my sap buckets over the years so I know they are
fond of the stuff. So it makes sense that they would be particularly active
during those periods when temps are mild and sap is flowing. Sugar maple
sap has the highest available sugar content and I assume would be the
"highest octane" fuel available to moths to power their flight and search
for mates.
Sugar maples (Acer saccharum) are common in the mountains where I live. I
also have red maples (A. rubrum) which are ubiquitous across the state; they
are one of the few trees that are abundant from the coast all the way up to
Mt Mitchell. I'm wondering if the pinions and sallows that others are
reporting from lower elevations are getting their sugar fix from red maple
sap. And there may be other trees exuding sap that are attractive to moths
as well. I know from syrup making that red maple sap also has sugar
content, just not as high a concentration. And red maples are also one of
the first trees to break bud and flower--usually in March here but in
February, sometimes as early as January, in eastern NC. I assume the
flowers are at least partially insect-pollinated and now I wonder if in
addition to sipping sap, moths might also be one of the dominant
pollinators.
Sorry to go so long. Just fascinating to me all of the ecological
connections between moths, plants, weather, syrup, and even the Northern
Arctic Oscillation. Either that or I've got a really bad case of spring
fever!
--
J. Merrill Lynch
Echo Valley Farm
Watauga County, NC
Elevation: 3,400 feet
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