Calvert County Dragonflies and Damselflies: Part Twelve – Skimmer Dragonflies of the Family Libellulidae

Family: Libellulidae (Skimmers)

Due to the large number of species present for the Family Libellulidae, I have been breaking down the family into smaller segments. This segment will focus on the Skimmer dragonflies which are all contained in a single genus Libellula.

Of the ten species listed below for southern Maryland from Richard Orr’s database, nine of the ten species can be found in all three southern Maryland counties. This includes two of the three species on the S3 Watch List of the Maryland Department of Natural Resources “List of Rare, Threatened, and Endangered Animals of Maryland”. In the iNaturalist database for the three southern Maryland counties as of March, 2020, species observations are as follows: Calvert – all 10 species, Charles – 9 species, and St. Marys County only 4 species recorded.

My contributions to the Calvert County iNaturalist database are as follows: entered a total of 44 observations of skimmers which included 8 of the 10 species present, but three of the eight species recorded were the result of a single observation. And of those three species, the Golden-Winged Skimmer and the Bar-Winged Skimmer are on the S3 Watch List and warrant a closer examination to insure proper identification. The Golden-Winged Skimmer was observed near the fresh water pond at Calvert Cliffs State Park which would be consistent with its expected habitat, but it can be difficult to differentiate from the Needham’s Skimmer dragonfly.

Listed below are the Skimmer species within the Libellulidae family that have been observed in at least one of the southern Maryland counties and a comparison of the two databases is made (as of March, 2020). As was done with the previous family, I have included with most species a note extracted from the book “Natural History of DelMarVa Dragonflies and Damselflies” by Hal White (reference 1). Of particular relevance for Calvert County, I have also included information on the four Pennant species of this family that were observed at the Cove Point LNG Property and reported in “2011-2012 Survey of the Dragonflies and Damseflies (Odonata) of the Cove Point LNG Property (Calvert County, Maryland” by Richard Orr (reference 2).

Golden-Winged Skimmer/Libellula auripennis
S3 Watch List (see below for definition)
This species is difficult to distinguish from the Needham’s Skimmer and it has not yet been confirmed on the DelMarVa peninsula. (1)
iNaturalist research grade observations:​ Calvert = 1 (May) St. Marys = 0 Charles = 2 (Jun)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – X Charles – present

Bar-Winged Skimmer/Libellula axilena
S3 Watch List (see below for definition)
This skimmer frequently selects perches on dead tree twigs, sometimes more than 20 feet above vernal ponds. (1).
Cove Point adult abundance and flight period – rare/14-Jun to 08-Jul. (2)
iNaturalist research grade observations:​ Calvert = 2 (May-Aug)​ St. Marys = 0​ Charles = 1 (May)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Spangled Skimmer/Libellula cyanea
Along the front edge near the tip of each wing of a dragonfly is a pigmented spot called the stigma. Because this feature is absent in many fossilized dragonfly wings, it is relatively new by geological standards and is presumed to be important. (1)
Cove Point adult abundance and flight period – common/19-May to 08-Jul. (2)
iNaturalist research grade observations:​ Calvert = 4 (Jun-Jul)​ St. Marys = 0​ Charles = 6 (Jun)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Yellow-Sided Skimmer/Libellula flavida
S2 Rare/S3 Watchlist (see below for definition)
Some 1920’s publications suggest that this species was once common on the Western Shore of the Chesapeake Bay, but certainly that is not the case today. (1)
Cove Point adult abundance and flight period – rare/24-May to 24-Jul. (2)
iNaturalist research grade observations:​ Calvert = 1 (Jul) St. Marys = 0 Charles = 2 (Jun-Jul)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present Charles - present

Slaty Skimmer/Libellula incesta
Dragonfly larvae breathe by constantly circulating water over rectal gills that line the inside of the abdomen and extract oxygen from the water. (1)
Cove Point adult abundance and flight period – common/04-Jun to 30-Sept. (2)
iNaturalist research grade observations:​ Calvert = 12 (Jun-Aug) St. Marys = 2 (May-Jul)​ Charles = 9 (Jun-Sept)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Widow Skimmer/Libellula luctuosa

Dragonflies that have emerged have small spiracles (holes) on the sides of their bodies where air enters a branching labyrinth of smaller and smaller tubes (tracheae). This enables oxygen to diffuse over a relatively short distance. (1)
Cove Point adult abundance and flight period – common/19-May to 11-Sept. (2)
iNaturalist research grade observations:​ Calvert = 11 (Jun-Jul) St. Marys = 4 (Jun-Sept)​ Charles = 8 (Jun-Sept)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles – present

Needham’s Skimmer/Libellula needhami

The species is named for James Needham, an entomology professor at Cornell University, by one of his students. It is abundant along salt marshes and rarely found at inland ponds. (1)
Cove Point adult abundance and flight period – abundant/19-May to 14-Oct. (2)
iNaturalist research grade observations:​ Calvert = 50 (Jun-Aug)​ St. Marys = 4 (Jun-Aug)​ Charles = 14 (Jun-Aug)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Twelve-Spotted Skimmer/Libellula pulchella

When a dragonfly locks onto a prey, it is able to adjust its flight so that it takes a direct line to an intercept point rather than a longer sweeping arc that would be generated by always flying directly toward the prey. (1)
Cove Point adult abundance and flight period – rare/17-Jun. (2)
iNaturalist research grade observations:​ Calvert = 1 (Jun)​ St. Marys = 0​​ Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles – present

Painted Skimmer/Libellula semifasciata
At their breeding sites, most dragonflies are territorial. Males find prominent perches overlooking the territory they will defend and normally return to that same perch after each time they fly out to challenge an intruder. (1)
Cove Point adult abundance and flight period – uncommon/04-May to 11-Sept. (2)
iNaturalist research grade observations:​ Calvert = 4 (May-Aug)​ St. Marys = 0​ Charles = 1 (Jun)
MD Biodiversity (i.e., Richard Orr): ​Calvert – present St. Marys – present​ Charles - present

Great Blue Skimmer/Libellula vibrans
In most years Great Blue Skimmers are scarce, but in wet years when woodland pools fill up with water in the spring and stay wet into the summer, Great Blue Skimmers are common. (1)
Cove Point adult abundance and flight period – uncommon/24-May to 11-Sept. (2)
iNaturalist research grade observations:​ Calvert = 26 (May-Aug)​ St. Marys = 4 (May-Aug) Charles = 19 (May-Sept)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Definitions from the Maryland Department of Natural Resources “List of Rare, Threatened, and Endangered Animals of Maryland”:
S2 - Imperiled / State Rare — At high risk of extinction or extirpation due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors. Typically occurring in 6-20 populations.

S3 - Vulnerable / Watchlist — At moderate risk of extinction or extirpation due to a fairly restricted range, relatively few populations or occurrences, recent and widespread declines, threats, or other factors. Typically occurring in 21-80 populations.

Publicado por rosalie-rick rosalie-rick, 16 de marzo de 2020

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