Calvert County Damselflies & Dragonflies: Part 18 – Bluet Damselflies of the Family Coenagrionidae

Family: Coenagrionidae (Bluets)

This is the third and final family of damselflies to be examined in this series of posts. Due to the large number of species present for the Coenagrionidae damselfly family, I have been breaking down this particular family into smaller segments. This grouping is comprised entirely of the genus Enallagma, the Bluets.

In Richard Orr’s Maryland database, there are eleven species of Bluet damselfly species listed as present in at least one of the three southern Maryland counties. Seven of those species are present in all three counties. All eleven species have been reported in Charles County with nine and seven species reported for St. Marys and Calvert Counties, respectively. Five of the eleven species are on the S3 Watch List.

The iNaturalist observation database for all damselflies in the southern Maryland counties is quite sparse and once again the same pattern continues with this group. There are only 10 research grade observations in total for the three counties and five of that total were submitted by me, all in Calvert County (Big Bluet x 4, Familiar Bluet x 1). They are the only Calvert County observations. St. Marys County has a single observation for each of two species (Big Bluet and Familiar Bluet), and Charles County has three observations total for two species (Big Bluet x 2, Orange Bluet).

Listed below are the species within this group 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 notes 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 six species 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).

Azure Bluet/Enallagma aspersum
Damselflies and dragonflies have large compound eyes that dominate the head. They also have three small, simple eyes that lie near the top and middle of the head. The extra eyes are called ocelli and are believed to provide close-up vision. (1)
Cove Point adult abundance and flight period – common/05-May to 11-Sept. (2)
iNaturalist research grade observations:​ Calvert = 0​ St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present ​ Charles - present

Double-striped Bluet/Enallagma basidens
The Double-striped Bluet represents one of the most dramatic range expansions in the US. Prior to 1930, it was unknown north and east of Texas. In just over 50 years it has expanded its range to the eastern US and as far north as New York. (1)
Cove Point adult abundance and flight period – uncommon/05-Jun to 11-Sept. (2)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present Charles - present

Familiar Bluet/Enallagma civile
Familiar Bluets feed away from water and hover over plants to pluck insects from leaves instead of catching them in flight. (1)
Cove Point adult abundance and flight period – abundant/04-May to 02-Dec. (2)
iNaturalist research grade observations:​ Calvert = 1 (Oct) St. Marys = 1 (Sept)​ Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present Charles - present

Attenuated Bluet/Enallagma daecki
S3 Watch List (see below for definition)
In the late 1800’s, damselflies were considered as a subgroup among dragonflies rather than the separate group equal to dragonflies as currently cataloged. (1)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – X St. Marys – present Charles - present

Turquoise Bluet/Enallagma divagans
S3 Watch List (see below for definition)
Adults can survive under water when ovipositing. Presumably the hairs on their thorax help to create a bubble of air that enables them to breathe underwater. (1)
Cove Point adult abundance and flight period – rare/16-Jun. (2)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr): ​Calvert – present St. Marys – present Charles – present

Big Bluet/Enallagma durum
S3 Watch List (see below for definition)
The Big Bluet is known for its salt tolerance and is common in freshwater estuaries along the northeastern Atlantic Coast. (1)
iNaturalist research grade observations:​ Calvert = 4 (Jul-Aug) St. Marys = 1 (Jun) Charles = 2 (Jun-Aug))
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Stream Bluet/Enallagma exsulans
The Stream Bluet is a delicate damselfly that prefers Piedmont streams, while most of its bluet relatives prefer ponds. (1)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – X St. Marys – X​ Charles - present

Skimmming Bluet/Enallagma geminatum
Studies of mitochondrial DNA from bluets indicate that the many species of bluets found in DelMarVa represent a recently evolving species swarm (a group of closely-related species), recently meaning the last period of glaciation. (1)
Cove Point adult abundance and flight period – rare/04-Jun. (2)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Orange Bluet/Enallagma signatum
Damselflies are often observed flying in tandem even after mating which assures that no other male can mate with the female. (1)
Cove Point adult abundance and flight period – common/03-Sept to 14-Oct. (2)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 1 (Sept)
MD Biodiversity (i.e., Richard Orr):​ Calvert – present St. Marys – present​ Charles - present

Slender Bluet/Enallagma traviatum
S3 Watch List (see below for definition)
Look for Slender Bluets in June and July in the vegetation along the shores of ponds. (1)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – X St. Marys – present Charles - present

Vesper Bluet/Enallagma vesperum
S3 Watch List (see below for definition)
Approximately 90% of dragonfly and damselfly species found in DelMarVa had been described by 1919, the year that the Vesper Bluet was first described. (1)
iNaturalist research grade observations:​ Calvert = 0 St. Marys = 0 Charles = 0
MD Biodiversity (i.e., Richard Orr):​ Calvert – X St. Marys – X​ Charles - present

Definitions from the Maryland Department of Natural Resources “List of Rare, Threatened, and Endangered Animals of Maryland”:
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, 08 de mayo de 2020

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