Voltinism

Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. Source Credit: Wikipedia.

Some species of odonates, such as Southern Spreadwing damselfly (Lestes australis), can be multivoltine.

Since the first official record of Southern Spreadwing damselfly at Huntley Meadows Park — a male spotted on 23 May 2014 in a drainage ditch near a vernal pool in the forest — the author has carefully monitored this location for the past two years. Henceforth, this location shall be referred to as the “study site.”

Field observations have shown one brood of Southern Spreadwing during Spring 2014 and Spring 2015; an individual from another probable brood of Southern Spreadwing was spotted during Fall 2015. Individuals from two broods of Southern Spreadwing were observed during Spring and Fall 2016.

Males

The following photo shows the only Southern Spreadwing observed at the study site during Spring 2016. This individual is a male, as indicated by his coloration and terminal appendages.

There are two vernal pools at the study site: the larger one is more like a small permanent pond that was formerly fishless; the smaller one is a true vernal pool and appears to be fishless. This individual was observed in a drainage ditch near the true vernal pool: the ditch is wet during spring/early-summer; dry in late-summer/fall.

Territorial Expansion

There is another vernal pool at Huntley Meadows Park that the naturalists refer to as the “Accidental Vernal Pool” because it was created by accident during the construction phase of the wetland restoration project. As it turns out, this pool is a good habitat for many species of odonates, including some species that prefer fishless water.

A male Southern Spreadwing was spotted at the “accidental vernal pool” on 26 May 2016; this is the first time this species has been observed in that location. It’s good to see the expansion of Southern Spreadwing territory, especially since it appears the habitat at the “study site” has been degraded by the introduction of fish to the larger pond.

One or more males were spotted the following day at the accidental vernal pool.

Female

A single Southern Spreadwing was observed at the study site during Fall 2016.

This individual is a female, as indicated by her coloration and terminal appendages.

I thought I had discovered a male Sweetflag Spreadwing damselfly (Lestes forcipatus) on 15 October 2015 at the study site. I made my speculative identification before I knew that Southern Spreadwings can be multivoltine. The observation and positive identification of a female Southern Spreadwing during the same month (in consecutive years) at the same location almost certainly means the species of the male I saw in 2015 was misidentified.

Editor’s Notes: Southern Spreadwing damselflies have been observed at two other locations in Northern Virginia: males from a single brood were observed during Spring 2016 at Meadowood Recreation Area; males and females from a single brood were observed during Fall 2016 at Mason Neck West Park. Further field observations are necessary to determine whether Southern Spreadwing is multivoltine at these sites.

Related Resource: Southern Spreadwing at MNWP, by Walter Sanford.

Copyright © 2016 Walter Sanford. All rights reserved.

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2 Responses to “Voltinism”

  1. Another new species of spreadwing damselfly? | walter sanford's photoblog Says:

    […] Post Update, 17 November 2016: New evidence strongly suggests the male spreadwing damselfly featured in this post is probably a Southern Spreadwing (Lestes australis) from another brood that emerged during Fall 2015. In 2016, Southern Spreadwing was confirmed to be multivoltine at the same location. […]

  2. Voltinism, revisited | walter sanford's photoblog Says:

    […] Some species of odonates, such as Southern Spreadwing damselfly (Lestes australis), can be multivoltine. Long-term monitoring of a vernal pool at Huntley Meadows Park has shown Southern Spreadwing is multivoltine at that site. […]

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