Summary

Did you know?

Most species of Striped Emeralds, dragonflies of the genus Somatochlora, have a metallic green wax coating their thorax (Dunkle 2000). The females of our species of interest, the Mocha Emerald, are slightly larger than the males (Natural Heritage Endangered Species Program 2003).

State Ranking Justification

The Mocha Emerald is known to occur in eight counties in New York State, with no population estimates determined. Further survey efforts may result in the identification of additional populations or range expansions, and may enable population size estimations.

Short-term Trends

No estimate of population size for the Mocha Emerald has been made between the early-1990s to 2002 (New York Natural Heritage Program 2007). Information prior to this time frame is even more limited. New location information on the Mocha Emerald in New York may reflect heightened interest in surveying for this species rather than a population increase or a range expansion (Holst 2005).

Long-term Trends

While recent observations of Mocha Emeralds have been made from the early-1990s to 2002 in Westchester, Rockland, and Orange counties, they are known to occur in Cattaraugus, Dutchess, Erie, Oswego, and Tompkins counties, as well as New York City based on earlier observations (Donnelly 2004, New York Natural Heritage Program 2007). Since the full extent and size of the populations have not been determined, long-term trends are unclear.

Conservation and Management

Threats

Any activity that might lead to water contamination or the alteration of natural hydrology could impact Mocha Emeralds and other stream dwelling odonates (Holst 2005). Such threats might include chemical contamination from agricultural run-off, changes in dissolved oxygen content, flow alteration, increases in sediment load, development near their habitats, and the building of dams (Natural Heritage Endangered Species Program 2003, Holst 2005).

Conservation Strategies and Management Practices

Any measures to reduce water contamination or hydrological alteration such as agricultural run-off, upland development, and damming that would affect flow of small forested streams should be considered when managing for this species (Holst 2005).

Research Needs

Further research is needed to define the distribution and population size of the Mocha Emerald. In addition, research is required to understand the habitat requirements and threats to this species, and to create appropriate management guidelines for its persistence in known locations (Holst 2005).

Habitat

Habitat

Mocha Emeralds inhabit small, shaded streams in forested areas that are about 1-3 yards wide with sand, gravel, or rocky substrates (Dunkle 2000, Nikula et al. 2003, Holst 2005). Larvae are aquatic and found in the water during this lifestage, whereas adults are terrestrial and are found in habitats surrounding forested streams.

Associated Ecological Communities

• Intermittent stream* (guide)
  The community of a small, intermittent or ephemeral streambed in the uppermost segments of stream systems where water flows only during the spring or after a heavy rain and often remains longer, ponded in isolated pools. These streams typically have a moderate to steep gradient and hydric soils. * probable association but not confirmed.
• Marsh headwater stream* (guide)
  The aquatic community of a small, marshy perennial brook with a very low gradient, slow flow rate, and cool to warm water that flows through a marsh, fen, or swamp where a stream system originates. These streams usually have clearly distinguished meanders (i.e., high sinuosity) and are in unconfined landscapes. * probable association but not confirmed.
• Rocky headwater stream* (guide)
  The aquatic community of a small- to moderate-sized perennial rocky stream typically with a moderate to steep gradient, and cold water that flows over eroded bedrock, boulders, or cobbles in the area where a stream system originates. * probable association but not confirmed.

Associated Species

• Ocellated Emerald (Somatochlora minor)
• Sable Clubtail (Stenogomphurus rogersi) (guide)

Range

New York State Distribution

The Mocha Emerald is confirmed in locations from eight counties in the eastern, central, and western parts of the state (Donnelly 2004, New York Natural Heritage Program 2007).

Global Distribution

The Mocha Emerald is distributed across North America from Ontario and the northeastern United States south to Florida, then west to the midwest and south to Texas (Dunkle 2000). It has a total known range from New York, New Jersey, Massachusetts, Connecticut, Rhode Island, Pennsylvania, Delaware, Maryland, Virginia, West Virginia, Kentucky, Tennessee, North Carolina, South Carolina, Florida, Georgia, Alabama, Louisiana, Mississippi, Missouri, Arkansas, Oklahoma, Kansas, Texas, Illinois, Indiana, Michigan, Iowa, and Ohio.

Best Places to See

• Beaver Pond Brook (Rockland County)

Identification Comments

Identifying Characteristics

Adult members of the family Corduliidae, or emeralds, have emerald green jewel-like eyes which come together to form a seam on top of their heads. Mocha Emeralds are large (2.3-2.6 inches), slender, and elegant dragonflies with black legs, a chocolate or mocha-colored thorax that has a greenish iridescence, and sometimes brown-tinted wings. They have a black abdomen with a whitish-yellow lateral (side) spot on abdominal segment 2 and pale orange-brown lateral (side) spots at the proximal ends (closest to the thorax) of segments 3-8. Male terminal appendages and female subgenital plates are distinctive among Somatochlora species when examined under magnification. Females (2.6-2.7 inches) are larger than males (2.3-2.4 inches), and their ovipositors are thorn-shaped and perpendicular from their abdomen. They are usually distinguished from other species of emeralds by their large size, elegant shape, brown-tinted wings, lack of markings on their thorax, and forested stream habitat.

Behavior

Adult Mocha Emeralds hunt and feed in nearby fields or forest undergrowth, sometimes hunting in pairs. Flight behavior can be rapid with up-and-down and side-to-side undulations or slower with gliding movements. Males patrol up to 20-30 yards of stream looking for females (Dunkle 2000). Females oviposit (lay eggs) alone after mating by tapping the tip of their abdomen directly into wet mud or shallow water at the edges of the stream (Natural Heritage Endangered Species Program 2003, Nikula et al. 2003).

Diet

Mocha Emerald larvae feed on smaller aquatic invertebrates and adults feed on insects which they capture in flight.

Best Time to See

Somatochlora linearis are active from late June through early September in the northeast (Nikula et al. 2003). They are most active in early morning, beginning at dawn, and in the late afternoon to dusk (Dunkle 2000). Larvae may be found in appropriate habitats year-round.

Similar Species

• Clamp-tipped Emerald (Somatochlora tenebrosa)
  If you look at the terminal appendages of a male Clamp-tipped Emerald from the side, there will be a circular gap between the appendages. This is distinctive from the Mocha Emerald and other emerald species. Female Clamp-tipped Emerald's have ovipositors (modified appendages used to pierce a substrate and lay eggs) that are longer than the length of abdominal segment 9, while the female Mocha Emerald's ovipositor is about as long as her abdominal segment 9. Both sexes of the Clamp-tipped Emerald have thoracic stripes, while the Mocha Emerald is lacking of any markings on its thorax.
• Williamson's Emerald (Somatochlora williamsoni)
  Male Williamson's Emeralds are darker brown than Mocha Emerald males. Females have ovipositors (modified appendages used to pierce a substrate and lay eggs) that are longer than the length of abdominal segment 9, while the female Mocha Emerald's ovipositor is about as long as her abdominal segment 9. Both sexes of the Clamp-Tipped Emerald have thoracic stripes, while the Mocha Emerald is lacking of any markings on its thorax.

Mocha Emerald Images

Somatochlora linearis
Blair Nikula

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Taxonomy

Mocha Emerald
Somatochlora linearis (Hagen, 1861)

• Kingdom Animalia
  • Phylum Arthropoda (Mandibulates)
    • Class Insecta (Insects)
      • Order Odonata (Dragonflies and Damselflies)
        • Family Corduliidae (Emeralds)

Additional Resources

References

Abbott, J.C. 2007. OdonataCentral: An online resource for the odonata of North America. Austin, Texas. Available at http://odonatacentral.com (accessed February 28, 2007).

Donnelly, T. W. 1992. The odonata of New York State. Bulletin of American Odonatology. 1(1):1-27.

Donnelly, T.W. 1999. The dragonflies and damselflies of New York. Prepared for the 1999 International Congress of Odonatology and First Symposium of the Worldwide Dragonfly Association. July 11-16, 1999. Colgate University, Hamilton, New York. 39 pp.

Donnelly, T.W. 2004. The Odonata of New York State. Unpublished data. Binghamton, NY.

Dunkle, S.W. 2000. Dragonflies Through Binoculars. A Field Guide to Dragonflies of North America. Oxford University Press: New York, New York. 266 pp.

Mead, K. 2003. Dragonflies of the North Woods. Kollath-Stensaas Publishing, Duluth, MN. 2003 pp.

Natural Heritage Endangered Species Program. 2003. Mocha emerald dragonfly (Somatochlora linearis). Massachusetts Division of Fisheries and Wildlife, Westborough, MA. Available http://www.state.ma.us/dfwele/dfw/nhesp (accessed February 28, 2007).

NatureServe. 2007. NatureServe Explorer: An online encyclopedia of life [web application]. Version 6.1. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer. (Accessed: January 11, 2007).

Needham, J.G., M.J. Westfall, Jr., and M.L. May. 2000. Dragonflies of North America. Revised edition. Scientific Publishers, Gainesville, Florida. 939 pp.

New York Natural Heritage Program. 2007. Biotics Database. Albany, NY.

New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.

New York State Department of Environmental Conservation. 2005. Comprehensive Wildlife Conservation Strategy Planning Database. New York State Department of Environmental Conservation. Albany, NY.

Nikula, B., J.L. Loose, and M.R. Burne. 2003. A field guide to the dragonflies and damselflies of Massachusetts. Division of Fisheries and Wildlife, Natural Heritage and Endangered Species Program, Westborough, MA. 197 pp.

Walker, E.M. 1958. The odonata of Canada and Alaska. Vol 2. The Anisoptera-four families. Univ. Toronto Press 318 pp.

Links

• Google Images
• NatureServer Explorer

About This Guide

Information for this guide was last updated on: April 16, 2007

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Somatochlora linearis. Available from: https://guides.nynhp.org/mocha-emerald/. Accessed March 23, 2023.