Volume VII, Number 2 - ISSN 1084-9750 - November 2000
This issue of Ode
News was put on the backburner for a while, as the editors worked
feverishly to complete a beginner’s guide to dragonflies and damselflies. The
manuscript is now at the publisher (Little, Brown, & Co.) with publication
scheduled for later this year. It will be a soft cover guide of 144 pages with
over 150 color photographs illustrating more than 100 of the most common and
widespread species in North America.
The world of odonate publications expanded dramatically during the last
half of 2000, with the appearance of two long-awaited books: Sid Dunkle’s Dragonflies
through Binoculars and the extensively revised manual Dragonflies of
North America by Needham, Westfall, and May. Reviews of both appear later in
this issue. Odonatists can now have at their fingertips exhaustive manuals to
both dragonflies and damselflies, a field guide to dragonflies, and a monumental
work on the behavior and natural history of odonates – quite a leap forward
from the relative dearth of publications just five years ago!
This issue of Ode
News focuses on the 2000 field season, a mediocre season at best. Water
levels were very low and the weather poor during much of the prime time (June
& July). These factors may have been responsible for what seemed to be very
low populations of many odonates, even such normally abundant and widespread
species as Eastern Forktails (Ischnura verticalis) and Common Green
Darners (Anax junius). The most exciting find came from Connecticut where
observers discovered the first regional records for Great Spreadwing (Archilestes
grandis); see Mike Thomas’ account on page 4.
Also in the pages that follow are articles by Jeremiah Trimble on his study of dragonfly congregations on the summit of Mt. Watatic and by Dick Hildreth on a surprising southbound movement of meadowhawks last fall.
CONTENTS
2000 Massachusetts Highlights
2000
Connecticut Highlights
Rhode
Island Update
Possible
Mass Movement of Meadowhawks in Massachusetts
Dragons
at the Summit
Massachusetts
State-Listed Odonates
Dragonflies through Binoculars
Dragonflies
of North America
New
Ontario Publication
Another
Ontario Publication
Corrigenda
About Ode News
The 2000 field
season in Massachusetts (and elsewhere in southern New England) was generally
rather slow, with few notable finds. Many species went unreported altogether.
A dry, nearly
snow-less winter and early spring resulted in a continuation of the drought
conditions of 1999 and very low water levels prevailed as we headed into the
2000 ode season. The early spring was very dry and warm (March rainfall was
about 5½” below average, while Boston temperatures averaged almost 5ºF above
normal), which apparently induced the early emergence of a number of species in
late April and May, and undoubtedly prompted the unprecedented late March
arrival of what was probably a Common Green Darner in Duxbury (erroneously
reported as April 1st in the last issue of Ode News).
Very wet weather
arrived in June, with rainfall in Boston (6.6”) nearly double the norm. The
weather dried out a bit in early July, but another long stretch of wet and cool
weather prevailed from mid-July into early August. Dry weather returned in
mid-August and continued into the fall. Although the wet weather early in the
summer replenished wetlands somewhat, water levels remained low throughout the
season. Whether due to depressed water levels and/or the heavy rains in June
(the prime emergence period for much of the local odonate fauna), many species
seemed to be in very low numbers in 2000. Whatever its impact on odonates, the
wet weather, much of which occurred on the weekends, certainly had a negative
impact on the activity of odonatists.
Observers:
Fred Goodwin, Rick Heil, Gail Howe, Jim MacDougall, Blair Nikula, Fred SaintOurs,
Jackie Sones, Jeremiah Trimble, Michael Veit. Letters in brackets following the
species name indicate Massachusetts state-listing designations: [E] = Endangered; [T] = Threatened; [SC] = Special Concern.
Lateral Bluet
(Enallagma laterale) [SC]: In addition to reports from coastal
sites, notable inland records of this species came from Moosehorn Pond Bog in
Hubbardston on 3 June where about 15 individuals were found (MV et al.),
and Tom’s Swamp, Petersham on the same date where a dozen or so were seen (BN et
al.).
Citrine Forktail
(Ischnura hastata): Normally scarce and local, this tiny yellow damselfly
seemed unusually widespread this season. As many as 25+ were present in late
August at a large, well-studied vernal pool in Eastham (JS et al.) where
the species has only rarely been found in the past. One at Gooseberry Neck,
Westport on 23 September (GH) was interesting, though this species is
surprisingly regular on islands well offshore. This species was also numerous in
Connecticut this year (see page 4). Did the low water levels favor this species?
The usually abundant Eastern Forktail (I. verticalis) was very scarce in
many areas this year. Did Citrine Forktails benefit from the paucity of their
larger congeners?
Mottled Darner
(Aeshna clepsydra): One at Gay Head on Martha’s Vineyard on 15 October
(JT et al.) was a first for Dukes County.
Lake Darner
(Aeshna eremita): The only record for this large darner came, once again,
from Mt. Watatic in Ashburnham where a single individual was netted on 13 July
(MV et al.). Of the several state records for this species, all but one
are from the summit of this mountain. Although there are several potentially
suitable lakes nearby, breeding by this species in the state remains
unconfirmed.
Spatterdock
Darner (Aeshna mutata)
[E]: This blue-eyed dazzler was found again at a number of sites in
northern Middlesex County (MV) and in Hampshire County (FM). One rather late
individual was netted on 8 July at Littleville Lake in Chester (MV et al.).
Subarctic Darner
(Aeshna subarctica): The only record for this late-flying, northern
darner came from a new site, a lovely bog in southern Ashburnham, where a single
male was netted on 9 September (BN). This discovery was particularly
encouraging, as the only other site known for the species in the state, a tiny
fen at the base of Mt. Watatic, has been flooded by beaver activity and may no
longer provide suitable habitat for this sphagnum inhabiting dragonfly. There
have been no records at this site since 1997.
Black-tipped
Darner (Aeshna
tuberculifera): One on Martha’s Vineyard in mid-September (JS) was another
first for poorly surveyed Dukes County.
Comet Darner
(Anax longipes) [SC]: We are aware of only a handful of sightings
for this conspicuous species in the state in 2000, all on Cape Cod.
Cyrano Darner
(Nasiaeschna pentacantha): The only report of this southern darner came
from Boston Brook/Pritchard’s Pond in Middleton where three were found on 4
June (RH).
Unicorn Clubtail
(Arigomphus villosipes): Two males at Bray Lake on Mt. Tom, Holyoke on 8
July (MV, BN) provided a first Hampden County record.
Spine-crowned
Clubtail (Gomphus
abbreviatus): A male captured on the Miller’s River in South Royalston on
17 June (MV), was the first for Worcester County and one of only a handful of
records from the state.
Harpoon Clubtail
(Gomphus descriptus) [E]: A single male at Littleville Lake,
Chester on 17 June (BN) was the only one reported this year.
Cobra Clubtail
(Gomphus vastus) [SC]: At least 70 freshly emerged individuals
were counted along a stretch of the Connecticut River in Sunderland on the
morning of 18 June (JT et al.). Heavy rains arrived later that morning,
soaking the observers and leaving them pondering the fate of these still weak,
incompletely developed tenerals.
Skillet Clubtail
(Gomphus ventricosus) [SC]: A single male near the Connecticut
River in Longmeadow on 17 June (BN) was the only report of this scarce species.
Southern Pygmy
Clubtail (Lanthus vernalis):
Two of these tiny gomphids were in Norwell on 25 May and several on 3 June (FS)
at a site where they’ve been found regularly in recent years.
Riffle Snaketail
(Ophiogomphus carolus) [T]: The only reports we received for this
bright green clubtail were from the Middle Branch of the Westfield River in
Chester where a single male was netted on 17 June (BN) and in Middlefield where
at least two males were present on 8 July (MV, BN).
Arrow Clubtail
(Stylurus spiniceps) [T]: An emerging male was found on the banks
of the Nashua River in Harvard on 15 July (JT et al.), a new site and
first modern Middlesex County record.
Arrowhead
Spiketail (Cordulegaster
obliqua): A male caught by an eleven year-old(!) in Ipswich on 3 June (fide
FG) was the only one reported in the state this year.
Ski-tailed
Emerald (Somatochlora
elongata) [SC]: The only record for this species this year came from
Mt. Watatic in Ashburnham on 13 July (MV et al.).
Forcipate
Emerald (Somatochlora
forcipata): A young male was captured on 16 June at a new site in Ashburnham
(MV). There are now five records (from four sites) for this northern dragonfly
in the state, the first in 1973, and the remainder all in the past four years.
Mocha Emerald
(Somatochlora linearis) [SC]: A teneral female caught on 5 July in
West Newbury (RH) was the only one reported.
Ebony Boghaunter
(Williamsonia fletcheri) [E]: This small, dark dragonfly was found
at three sites in Massachusetts this year. About 10 tenerals, both males and
females, were found at a bog in Ashburnham on 14 May (MV), a new site for the
species in the state. A single male was found at Moosehorn Pond in Hubbardston
on 27 May (MV), where the species was known from just one previous record in
1991. Several individuals were present again at Tom’s Swamp in Petersham on 3
June (BN, JT et al.).
Hudsonian
Whiteface (Leucorrhinia
hudsonica): Two in Ipswich on 30 April (JM) represented a long overdue first
for Essex County.
Elfin Skimmer
(Nannothemis bella): This tiny bog denizen was present again in numbers
at the Lake Wampanoag bog in Ashburnham (MV, BN et al.).
Spot-winged
Glider (Pantala hymenaea):
Two at Belle Isle marsh in East Boston on 15 July (RH) provided an overdue first
record for poorly surveyed and heavily urbanized Suffolk County.
Very few evening
swarms of dragonflies were noted in 2000. One of the few occurred on 7 August at
the Mill Pond Conservation Area in West Newbury where roughly 300 individuals
included three Canada Darners (Aeshna canadensis), 12 Lance-tipped
Darners (A. constricta), three Black-tipped Darners (A. tuberculifera),
four Green-striped Darners (A. verticalis), 125+ unidentified mosaic
darners (Aeshna spp.), 125+ Common Green Darners (Anax junius),
four Clamp-tipped Emeralds (Somatochlora tenebrosa), eight unidentified
striped emeralds (Somatochlora spp.), three Spot-winged Gliders (Pantala
hymenaea), and two Black Saddlebags (Tramea lacerata).
Migrants:
Inveterate hawkwatcher Tom Carrolan provided a couple of dragonfly migration
reports from Massachusetts this year. On 10 June he counted 453 northbound
individuals over seven hours at Pilgrim Heights in Truro. Although he was unsure
of the species, that same day a few miles south in Wellfleet, Jackie Sones noted
numbers of Spot-winged Gliders (Pantala hymenaea) moving north. On 13
September, while hawkwatching at Salisbury Beach (just south of the New
Hampshire border), Tom witnessed a substantial movement of southbound
dragonflies (again, species unknown, but this time most likely Common Green
Darners). Based upon a series of one minute sample counts, he estimated about
900/hour passing during the late morning, increasing to 1500+/hour from 2:00 –
4:00 p.m.
Brian Cassie and
others from the Massachusetts Butterfly Club made systematic counts of migrant
butterflies along the coast of Westport this fall, primarily at Gooseberry Neck.
In the process they recorded numbers of migrant dragonflies. The only date upon
which a significant movement was seen was 22 September when Brian counted 1438
Common Green Darners (Anax junius), 205 Black Saddlebags (Tramea
lacerata), 1 Carolina Saddlebags (T. carolina), and 13 Wandering
Gliders (Pantala flavescens).
Mike Thomas
For many
individuals, the highlight this season was the opportunity to observe several
very cooperative adult Ringed Boghaunters (Williamsonia lintneri)
during the University of Connecticut Dragonfly and Damselfly Workshop field trip
held this past May (for details see Argia 12[3]:8). With adrenalin flying high,
participants left the workshop anxious to test their new skills in the field.
Unfortunately, good intentions were hampered by above average rainfall, with
some parts of the state receiving over 8” of rain during the month of June.
With rivers and
streams near or above capacity, adult gomphids at times seemed scarcer than
Ringed Boghaunters, with emergence delayed by at least a week compared to past
seasons. On 27 May, several Brook Snaketail (Ophiogomphus
aspersus) larvae were collected from sandy pockets behind boulders in Sandy
Brook (Litchfield County), although not one adult was observed patrolling over
the stream in the weeks to follow. On 11 June, one eclosing Cobra Clubtail
(Gomphus vastus) was found on a tree trunk along the Connecticut River in
the vicinity of Kings Island (Hartford County). Most emergence sites (e.g.,
mossy river banks, tree trunks) were completely submerged, and along with the
swift current, made searching for exuviae a very difficult and unproductive
activity. Robert Muller observed several territorial Spine-crowned Clubtails
(Gomphus abbreviatus) on the Mill River in Hamden (New Haven County) on 9
& 10 June. Along the Hollenbeck River (Litchfield County), Dave Wagner and
Mike Thomas located three adult Harpoon Clubtails (Gomphus descriptus)
perching on the ground in a corn field on 24 June. For whatever reasons,
perhaps due to last year’s drought conditions or this year’s heavy rains,
there seemed to be a lack of adult gomphid
activity on many of our streams and rivers.
Both Stygian
and Umber Shadowdragons (Neurocordulia yamaskanensis & N.
obsoleta) seemed unaffected by the heavy rains, and were again seen along
the Connecticut River in Cromwell (Middlesex County) during late June and early
July.
Several species
appear to be expanding their range in Connecticut, perhaps due to global
warming. Prior to this year, all of our records for the Citrine Forktail
(Ischnura hastata) were from coastal localities. This year, not only was
this species especially abundant along the coast, it was reported well inland
for the first time. One of the more bizarre records was a single male captured
in a malaise trap set in a sandy grassland located in northern New Haven County.
Spatterdock Darners (Aeshna mutata) also had a banner year, with
several new sites documented from Norfolk and Canaan (Litchfield County),
representing
our first records from the northwest corner of the state. Of note was a swarm of
up to five individuals feeding on insects along the edge of a corn field on 24
June (MCT & DLW).
Surprises come when you
least expect them, and this year was no exception. Of the 21 odonate species
recorded during a Biodiversity Day held in Madison on 9 September, the most
exciting discovery was a male Great Spreadwing (Archilestes grandis)
collected by Clay Taylor. This finding not only represents a new state
record, it is the first time this species has been documented from southern New
England. In the last issue of Ode News (Volume VII, Number 1), Blair
Nikula included this species in a list of potential invaders to be sought in our
area. Two other sites have since been discovered. On 22 September, Andy Brand
captured a second male from a field in Hamden (New Haven County) and on 30
September, Chris Maier and Mike Thomas observed up to six males and females at
Lake Gaillard (New Haven County), a large manmade impoundment with little, if
any, emergent vegetation. Both males and females were observed hanging from
vegetation in typical lestid fashion along wooded glades several hundred yards
from the impoundment.
On the Northeastern
Odonate listserv, Bill Yule provides an account of an impressive migration of Common
Green Darners (Anax junius), numbering in the thousands, along the
dunes of Hammonasset State Park on 15 October. The same day, Noble Proctor and
Margaret Ardwin observed this flight on the coast just to the west. At Jacob’s
Beach in Guilford during the late morning, they estimated green darners passing
at the rate of over 10,000/hour (based upon a series of one-minute counts). At
Ox Pasture in Madison, from noon to 1:00 pm, their sample counts resulted in
estimates of up to an astounding 120,000/hour! They also noted hundreds of
Yellow-legged Meadowhawks moving (see article by Dick Hildreth on page 6).
The former Ginger
Carpenter — now Ginger Brown following November nuptials (Congratulations,
Ginger!) — took a moment from her hectic schedule to provide some highlights
from the Rhode Island Odonate Atlas’ 2000 field season. The atlas completed
its third year, receiving over 2000 records for the year, and turned up one new
species, bringing the state total to 130 species.
Several new records
were found for Attenuated Bluet (Enallagma daeckii), New
England Bluet (E. laterale), Scarlet Bluet (E. pictum),
and Pine Barrens Bluet (E. recurvatum). Especially interesting
was the discovery of the latter two species on a stretch of quiet backwater on
the Pawtuxet River. These species are typically associated exclusively with
coastal plain ponds, though Ginger reports that this stretch of the river
botanically is very similar to such ponds. Most exciting among the damselfly
reports was the discovery in mid-July of a second population of Blackwater
Bluet (E. weewa) in Charlestown along a small, sluggish, tannin-rich
stream. Additionally, a specimen collected at a lake in South Kingston in 1999,
and initially identified as a Stream Bluet (E. exsulans), proved upon
reexamination also to be a Blackwater Bluet. Thus, this southern damsel is now
known from three sites in Rhode Island, two small streams and a lake. There are
no other New England records.
Comet Darners
(Anax longipes) were found at two or three new sites, and there were
three records of Spatterdock Darner (Aeshna mutata). Clubtails
were scarce (as elsewhere in southern New England), but two records of Lilypad
Clubtail (Arigomphus furcifer) represented the first during the atlas
period. Two occurrences of American Emerald (Cordulia shurtleffii)
were the first for the Ocean State. Single Beaverpond Baskettails (Epitheca
canis) and Spiny Baskettails (E. spinigera) represented just
the second record for each from the state. Another Coppery Emerald (Somatochlora
georgiana) was found, the only one of this rare southern emerald found in
New England in 2000.
Once again,
extensive field work was conducted on the imperiled Ringed Boghaunter (Williamsonia
lintneri) in Rhode Island. At one site, Ginger and her co-workers recovered
586 exuviae, by far the most ever recorded for this inconspicuous species.
However, there was considerable mortality at this site, most likely
weather-related. Emergence, first noted on 10 April, occurred on some cold
(low-mid 40s ºF), wet days and some tenerals apparently expired right on the
spot. Of far greater concern, this site, home to the largest known population of
Ringed Boghaunter, has been severely impacted by a sand and gravel mining
operation which has destroyed much of the upland habitat adjacent to the
wetland.
Possible Mass Movement of Meadowhawks in Massachusetts
Richard Hildreth
On 13 October 2000,
I hiked along a power line in Milford, Massachusetts, from Route 85 southeast to
Route 16 and back. This transverse (about 2.6 miles round trip) passes over an
area of mostly dry, upland, rocky country, underlain by the Milford Granite. The
granite is criss-crossed by many faults. Fractured rock along several of the
major faults was removed by glacial action leaving linear valleys. In these
valleys are some small wetlands; red maple swamps in the forested country beside
the power line, shrub swamps along the power line right-of-way.
My major purpose
for the trek was to look for migrating butterflies. By this date, almost all of
the flowers were “gone by” and there was little butterfly activity. I saw
only two migrating butterflies, both Mourning Cloaks flying rapidly southwest.
I was also looking
to see what odonates might by flying on that date. Right away I saw a few
meadowhawks (Sympetrum sp.) flying and perching in warm sunny spots. I
saw one Common Green Darner (Anax junius) in apparent migratory flight
toward the southwest. I also saw five mosaic darners patrolling in the area; I
netted two of these and they turned out to be Shadow Darners (Aeshna umbrosa).
I noticed a pair of
meadowhawks in the towing mode (male clasping the female) flying rapidly across
the power line. Soon I saw more pairs in tandem, all flying southwesterly. They
were flying rapidly about 6–15 feet above the ground. When they reached the
forest at the edge of the power line right-of-way, they flew up and over the
trees and continued on toward the southwest. Along the power line, close to
Route 16, is a small quarry hole with a pond. I stopped to look at this pond and
saw several tandem pairs of meadowhawks flying around the pond. I expected to
see the females depositing eggs on the water or along the damp shore. Instead, I
saw tandem pairs flying in from the northeast, dropping down into the quarry
pond, flying around a bit “checking it out,” then departing off to the
southwest. During my trek, I saw 24 pairs flying toward the southwest and none
in any other direction. They were all flying high and fast and I was unable to
catch any.
On 14 October, I
visited the same power line, but on the other side of Route 16. During this very
short visit I saw four tandem pairs flying southwest. This time I managed to net
one of the pairs and they proved to be Yellow-legged Meadowhawks (Sympetrum
vicinum). I had studied those seen the previous day through 10X binoculars
and they also seemed to be this species (females have a distinctive
trumpet-shaped ovipositor which can sometimes be seen with binoculars).
On 15 October, I
visited Plum Island (Essex County) on a Forbush Bird Club trip. I noticed nine
tandem pairs of meadowhawks flying southwestward. They were all flying rapidly
in a direct, “determined” fashion. I watched several of them fly out over
the salt marsh on the west side of Plum Island.
Editor’s
Note: Dick
Hildreth’s observations coincide with similar reports received over the
Internet from the Connecticut coast and from New Jersey, involving even larger
numbers of meadowhawks. On 15 October at Hammonasset Beach State Park on the
Connecticut coast, Bob Yule saw hundreds of meadowhawks (species uncertain)
moving, many of them in tandem. The same day, just to the west, Noble Proctor
and Margaret Ardwin, saw hundreds of Yellow-legged Meadowhawks, mostly pairs in
tandem, moving along the coast in Madison and Guilford. Also on the 15th,
about 20 miles to the west, Bob Muller estimated thousands (based upon a series
of one-minute counts) passing through his yard in Milford, CT between the hours
of 2:00 – 5:00 p.m. North American meadowhawks, other than the western
Variegated Meadowhawk (Sympetrum
corruptum), generally have not been considered migratory. The movement of so
many pairs in tandem is also curious and puzzling. However, southwesterly
movements of tandem pairs in the fall has been observed before in southern
Ontario. Large numbers were recorded there in 1996, with lesser numbers in 1998
(see Argia, 9[1]:19-21 & 10[4]:19-22). Time will tell whether this is
a regular phenomenon (perhaps in response to drought conditions?).
Jeremiah Trimble
During the summer of 1999,
I had an opportunity to research dragonfly behavior for my senior’s honor’s
thesis at Connecticut College. Studying dragonflies has become an intense hobby
of mine and over the last few years I have visited many places throughout New
England and North America looking at dragonflies. One of the most fascinating
sites I have visited is Mt. Watatic in Ashburnham, Massachusetts. During visits
to Mt. Watatic, hundreds of dragonflies, mostly mosaic darners (Aeshna spp.),
and smaller numbers of striped emeralds (Somatochlora spp.) can be seen
cruising around the rocky summit. I found it intriguing that such high numbers
of darners were concentrated in such a small area, while relatively few were
seen in nearby areas. I designed a study to look at this phenomenon, hoping to
solve the mystery of why dragonflies were congregating on the mountaintop.
Two possible hypotheses
were devised for the congregations of dragonflies on Mt. Watatic. The first
hypothesis suggested that the dragonflies were “hilltopping.” Certain orders
of insects (such as the Diptera and Lepidoptera) have been shown to converge on
hilltops in order to increase mating success. In other words, mature individuals
of a species move to the highest points in the landscape. By doing this they
become more concentrated as they occupy a smaller area, and it becomes more
likely that a male and a female of that species will find each other. This is
probably most important in species with low population densities. In a
hilltopping situation one would expect nearly all of the mature individuals to
congregate at the highest point, otherwise the mechanism would not be as
effective. The second hypothesis suggested that these dragonflies were
converging on Mt. Watatic in order to feed. Many dragonflies, especially darners
and emeralds, feed in open habitats such as meadows. Thus, the summit of Mt.
Watatic might represent an excellent feeding habitat for them.
In order to test these
hypotheses, four study plots were established at intervals along an abandoned
ski slope that stretches from the summit of Mt. Watatic to its base. Dragonfly
abundance and meteorological data (temperature, light intensity, wind speed, and
humidity) were recorded at each plot throughout the summer to determine (1)
whether elevation affected dragonfly abundance and (2) whether various weather
conditions affected dragonfly abundance. I also spent time recording time
budgets for individual dragonflies: watching an individual dragonfly for one
minute and recording the amount of time it spent at various activities such as
feeding, mating, and resting. I spent many days on Mt. Watatic catching as many
dragonflies as I could and recorded the number and sex of each species. I found
five species of mosaic darners, with Variable Darner (Aeshna interrupta)
by far the most numerous, and four species of striped emerald. The sex
ratio on the mountaintop was very close to 50:50. Finally, I studied relative
prey densities in the various plots. This was done by setting out insect traps,
which consisted of aluminum pie pans with a sticky substance spread on them
(makeshift fly paper), in the four plots for eight hours each day. I brought
them in at the end of the day and counted the number of insects captured and
recorded the order to which each belonged.
Some interesting findings
came out of the meteorological data. There was a significant positive correlation
between dragonfly abundance and both temperature and light intensity. The hotter
and brighter the day became, the more dragonflies were seen in the plots. This
reached a threshold, however, at about 30ºC (86ºF). At such high temperatures
and light intensities, perhaps the dragonflies were unable to thermoregulate and
retreated to shaded areas. There was no correlation between dragonfly abundance
and humidity or wind speed.
The data I collected
supported the feeding hypothesis rather than the hilltopping hypothesis.
Although numbers of dragonflies increased significantly as elevation increased,
they were found at all of the study plots. My time budget study showed that the
darners were spending nearly 100% of their time feeding and no time mating. The
50:50 sex ratio also did not support the hilltopping hypothesis. In a
hilltopping situation one would expect there to be many more males than females
congregating on the hilltop, with females appearing only briefly to mate and
then move on. Also of note was that no mating behavior was observed during the
study (although in past years, mated pairs of darners have occasionally been
seen on the mountaintop). The findings from the prey density study supported the
feeding hypothesis. The number of prey items increased with elevation and the
number of dragonflies was positively correlated with relative prey density
(though these correlations were not statistically significant). That is, the
more prey there was, the more dragonflies were present. Small dipterans made up
the majority of insects captured in the traps and they appear to make up a large
part of dragonfly diets (though I was unable to determine what the dragonflies
on Mt. Watatic were feeding upon).
Although dragonflies on
Mt. Watatic exhibited a significant tendency to concentrate at the summit, the
results of this study suggest they were doing so not to find mates, but rather
to take advantage of a food supply that increased with elevation. So, despite
exhibiting a hilltopping-like behavior, it was not consistent with hilltopping
as it previously has been defined (i.e., to increase mating success).
Hilltopping may still play an indirect role in the Mt. Watatic situation, as it
is possible that these dragonflies are taking advantage of the hilltopping
behavior of other insects in order to increase their foraging efficiency.
Why are these dragonflies
apparently not hilltopping to increase mating efficiency? Previous observations
and studies have shown that dragonflies in most cases return to their aquatic
habitat to mate. In general, males set up a territory or patrol the habitat in
search of a potential mate. Carrying out these behaviors at the aquatic habitats
is beneficial as in most cases this is also where the eggs will be laid and the
larvae develop. It might not make as much sense for dragonflies to mate on the
hilltop, as the travel time back to the wetland could introduce increased
mortality of females. Congregating at the breeding site to find a mate, breed
and lay eggs seems to be a very efficient life cycle for dragonflies. Why, then,
don’t butterflies meet at patches of the caterpillar host plants to find mates
and carry out the rest of the life cycle? Well, many species of butterflies may
do just that. However, in some cases, as in those species known to be “hilltoppers,”
the larval food plants may be so spread out that mate finding is very
inefficient. Thus, a mechanism might develop to increase mating efficiency (i.e.,
hilltopping). In such cases, the benefits of congregating presumably outweigh
the risks of traveling to the hilltop and back to the breeding site.
Of course, there is still
a lot to be learned about this phenomenon. It is unknown how widespread this
behavior is in New England, or elsewhere. It would be interesting to learn about
other occurrences.
Massachusetts
State-Listed Odonates
With the recent addition of Rapids Clubtail (Gomphus quadricolor),
there are now 27 species of odonates listed by the Natural Heritage &
Endangered Species Program as either Endangered (10 species), Threatened (4
species), or Special Concern (13 species) in Massachusetts. This represents
about 16% of the 165± species known from the state.
Of the 49 species of damselflies, only four (8%) are listed (all bluets).
Twelve (almost half) of the listed species are clubtails (Gomphidae), while
another eight species are emeralds (Corduliidae). These totals represent 44% and
35% of the clubtails and emeralds, respectively, known from the state. In sharp
contrast, none of the skimmers (Libellulidae), the most diverse family in the
state (41 species), is state-listed.
Family Coenagrionidae (Pond Damsels):
Tule Bluet (Enallagma carunculatum) - SC
Attenuated Bluet (Enallagma daeckii) - SC
New England Bluet (Enallagma laterale) - SC
Pine Barrens Bluet (Enallagma recurvatum) - T
Dragonflies (Anisoptera)
Family Aeshnidae (Darners):
Spatterdock Darner (Aeshna mutata) - E
Comet Darner (Anax longipes) - SC
Ocellated Darner (Boyeria grafiana) - SC
Family Gomphidae (Clubtails):
Spine-Crowned Clubtail (Gomphus abbreviatus) - E
Beaverpond Clubtail (Gomphus borealis) - SC
Harpoon Clubtail (Gomphus descriptus) - E
Midland Clubtail (Gomphus fraternus) - E
Rapids Clubtail (Gomphus quadricolor) - T
Cobra Clubtail (Gomphus vastus) - SC
Skillet Clubtail (Gomphus ventricosus) - SC
Brook Snaketail (Ophiogomphus aspersus) - SC
Riffle Snaketail (Ophiogomphus carolus) - T
Riverine Clubtail (Stylurus amnicola) - E
Zebra Clubtail (Stylurus scudderi) - E
Arrow Clubtail (Stylurus spiniceps) - T
Family Corduliidae (Emeralds):
Umber Shadowdragon (Neurocordulia obsoleta) - SC
Lake Emerald (Somatochlora cingulata) - SC
Ski-tailed Emerald (Somatochlora elongata) - SC
Coppery Emerald (Somatochlora georgiana) - E
Kennedy's Emerald (Somatochlora kennedyi) - E
Mocha Emerald (Somatochlora linearis) - SC
Ebony Boghaunter (Williamsonia fletcheri) - E
Ringed Boghaunter (Williamsonia lintneri) - E
Dragonflies through Binoculars
Sidney Dunkle.
2000. Oxford University Press.
Facing each plate
are brief, concise species descriptions, as well as range maps. The maps are
small but give a good sense of the range of each species and, given that they
are the first odonate maps to appear in print, are another very valuable feature
of the guide. The maps are also color coded to indicate, in a very general
sense, each species’ flight season (i.e., spring, summer, fall, or
year-round).
The species
accounts, drawing upon the author’s extensive experience and discerning eye,
contain a wealth of useful information. The Comments sections supplement the
Identification sections with useful behavioral information. Although the guide
is geared to identification through binoculars (i.e., not in the hand),
the author occasionally includes features that are visible only in the hand (and
in some cases, only under a microscope). Yet, there is no discussion of catching
dragonflies for closer inspection. This incongruity apparently results from the
author’s desire to be thorough conflicting with the series editor’s aversion
to collecting, or even catching and releasing odonates. The inescapable fact is
that many species of dragonflies simply are not identifiable except in the hand,
and, unlike butterflies, generally can be handled without harm. Avoiding the
issue of occasional in-the-hand examination does the reader — especially the
beginner — a disservice.
So, was it worth
the wait? Absolutely! Could it have been better? Certainly (and had the author
not had restrictions placed upon his efforts, undoubtedly would have been). But
whatever its shortcomings, Dragonflies through Binoculars is a monumental
achievement and a significant addition to the rapidly growing body of literature
on North American odonates. Everyone interested in these creatures should own a
copy or two (one for the bookshelf, one for the car). I look forward to giving
it a good workout in 2001. Hats off to Sid Dunkle!
(Rumor
has it that Sid has begun work on a damselfly guide – another round of
anticipation begins!)
James G. Needham,
Minter J. Westfall, Jr., &
In 1955, James
Needham and Minter Westfall co-authored Dragonflies of North America, the
first comprehensive manual to the identification of North American Anisoptera.
For 45 years this stood as the one and only identification reference. It was an
intimidating tome to the beginner, and for at least a few (this writer included)
dissuaded further pursuit of the subject!
Some years ago, Mike May undertook a complete revision of this landmark
publication – a massive undertaking, but one accomplished with great success.
The revised manual covers 350 species recorded from northern Mexico through
Canada. Extensive keys are included for the families as well as genera, and for
many species the male anal appendages and various other body parts significant
for identification are illustrated, either with black-and-white photos or line
drawings.
The 46-page
introduction includes thorough descriptions of the anatomy of both adult and
larval dragonflies, as well as sections titled Field Studies, Preservation and
Curation Techniques, and Suggestions for Users of This Manual, and concludes
with a 5-page checklist of the species included. A nice, and welcome addition
from the first edition is 24 full-color plates: 14 plates of illustrations by
Lawrence Zettler and 10 plates of photos. The illustrations are of lateral views
only, but are nicely done and include four plates of Aeshnidae (36 species),
seven of Gomphidae (~90 species), one of Cordulegastridae (8 species), and two
plates of Corduliinae (25 species). Color copies of these would be a useful
addition to any odonatist’s field pack. In some cases, the colors of the
illustrations seem a bit gaudy (e.g., the lateral thoracic stripes on the
Nasiaeschna pentacantha are much too bright and green). I find the
facing-page keys to the illustrations to be quite confusing in many cases, as
the species name often does not line up with the appropriate illustration. The
73 photos on 10 plates illustrate the major genera and a few life history
stages, and are generally well reproduced.
The species
accounts occupy 748 pages and include extensive, “stem to stern,”
descriptions of each species. These accounts are not intended to aid in field
identification, rather being geared to in-the-hand or under-the-microscope
examinations. Natural history information, aside from an occasional, very brief
comment in the introductory sentence, is lacking. (There is one notable
taxonomic change from the previous edition and most other publications to date:
the cruisers and emeralds are treated as belonging to the subfamilies
Macromiinae and Corduliinae, respectively, within the Libellulidae, rather than
separate families, Marcomiidae and Corduliidae.) The book concludes with a
13-page checklist to the species by region, a 14-page glossary, a 27 page
bibliography (nearly 600 citations), and indexes to both the scientific and
common names.
Although still intimidating, the extensive visual enhancements make this manual more “user friendly” than its predecessor. Mike May has done the odonatological community a great service. This publication belongs on the bookshelf of every serious odonatist.
A new publication
on the odonates of Ontario is now available: Damselflies and Dragonflies
(Odonata) of Ontario: Resource Guide and Annotated List by P. M. Catling and
V. R. Brownell. The book is 198 pages, with complete species accounts, dot maps,
and identification keys. It is also liberally illustrated with drawings of
anatomical details useful for identification. The book can be ordered directly
from the authors (2326 Scrivens Drive, R.R. 3, Metcalfe, Ontario, K0A 2P0;
email: brownell@achilles.net). The price is $28.00 plus $6.00 shipping, Canadian
funds.
The folks in
Ontario have been busy! Ontario Odonata, Volume 1, edited by Paul M.
Catling, Colin Jones, and Paul Pratt, was recently published by the Toronto
Entomologists Association. Contained within its 153 pages are a variety of
interesting articles covering such subjects as the conservation status of
odonates in Ontario, the status of particular species in the province, surveys
from specific regions, dragonfly migration along the Lake Ontario shoreline, a
garter snake preying upon a dragonfly, and a key to the nymphs of hanging
clubtails (Stylurus). The bulk of the publication, nearly 90 pages, is
devoted to records from the 1999 field season, presented in a tabular format —
over 3,600 records total! The editors describe this as the “first annual,”
suggesting that additional volumes will appear regularly. They have established
a high standard to maintain!
Ontario Odonata
is available for $20.00 (U.S. funds). To order, send a check to: Toronto
Entomologists Association, c/o Alan Hanks, 34 Seaton Drive, Aurora, Ontario, L4G
2K1.
In the last issue
of Ode News (Vol. VII, #1) we reported an extremely early dragonfly,
probably a migrant Common Green Darner, at Duxbury Beach on the first of April.
The date was actually 31 March 2000 – making it the first March odonate ever
recorded in the state (and, as far as we know, New England)!
Also in the last issue, we identified the dragonfly in the photo below as a Yellow-sided Skimmer (Libellula flavida). It is, in fact, a Bar-winged Skimmer (Libellula axilena), identifiable by the dark bar on the outer leading edge of the forewing and the small, gray patch at the base of the hindwing. Thanks to Sid Dunkle for calling our attention to this error. Now that Sid’s guide is out, we no longer have any excuses for such misidentifications!
Editorial Staff & Production…Blair Nikula and Jackie Sones
Illustrations…Fahy Bygate, Jackie Sones, and Jeremiah Trimble
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