Four-spot midget (Mortonagrion hirosei)

Description

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Four-spot midget fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Four-spot midget description

With four apple-green spots on its black back, the four-spot midget is a very distinctive and attractive damselfly ^{(2) (3)}. Females may be one of two forms, and whilst some are like the previous description, others are orange. Immature four-spot midgets are greyish but still have four pale spots visible on the back ⁽²⁾. Like other damselflies, the four-spot midget has a long, slender body, richly-veined wings that are held vertical at rest, and large eyes which provide exceptional vision ⁽⁴⁾.

Size

Length: up to 2.5 cm ⁽²⁾

Four-spot midget biology

All damselfly larvae live in water, where they breathe through external gills ⁽⁶⁾. The larvae are opportunistic hunters, feeding on a wide range of invertebrates ⁽⁴⁾. They capture their prey by stalking it until they are sufficiently close to shoot out their labium (lower jaw), which bears hinged hooks to impale the prey and drag it back into the damselfly’s mouth ^{(4) (6)}.

Near the end of their larval life, the larvae stops feeding and moves to a plant, rock or other substrate and begins to breathe air ^{(4) (6)}. The adult body bursts through the larval skin, the wings expand and harden, and the insect takes its first flight ⁽⁶⁾. Unlike many damselflies, the four-spot midget does not leave the site in which they emerged, and instead will stay in the reed community where they will spend their entire adult life ⁽⁵⁾.

Adult four-spot midgets can be seen flying about their habitat from late May to early August ⁽⁵⁾. Like the larvae, the adults are generalized, opportunistic feeders ⁽⁴⁾, which prey on smaller flying insects, such as midges and mosquitoes ⁽²⁾. The four-spot midget is a weak flier, and adopts a sit-and-wait tactic when searching for prey or mates ⁽⁵⁾. Its weak flying abilities, along with its small body size and bright colouration, especially of the males, may mean it is particularly vulnerable to predation. The average lifespan of this damselfly is estimated to be around 35 days ⁽⁵⁾.

Four-spot midget range

Occurs in Japan, Hong Kong and Taiwan. It may also exist in mainland China ⁽²⁾.

Four-spot midget habitat

Four-spot midgets inhabit brackish streams and marshes ^{(1) (5)}, where the larvae occur in the water and the adults inhabit reedbeds ⁽⁵⁾.

Four-spot midget status

The four-spot midget is classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾.

Four-spot midget threats

This vulnerable insect is threatened by habitat loss and degradation ⁽¹⁾. In Japan, the extent of reedbeds has been substantially reduced by river alterations and the destruction of wetlands ⁽⁵⁾, and suitable habitat in mainland China is similarly being lost to city development, reclamation and dam construction ⁽²⁾.

Four-spot midget conservation

The four-spot midget occurs in at least one protected area, the Mai Po Nature Reserve in Hong Kong. Research projects on the four-spot midget are being carried out to improve understanding of this species and reedbed re-establishment programmes are being undertaken ⁽²⁾. The IUCN, which have assessed the four-spot midget as Vulnerable to extinction, recommend that the coastal breeding sites of this attractive damselfly are protected ⁽¹⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For further information on damselflies see:

• O’Toole, C. (2002) The New Encyclopedia of Insects and their Allies. Oxford University Press, Oxford.

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Glossary

Brackish

Slightly salty water.

Invertebrates

Animals with no backbone.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

References

1. IUCN Red List (June, 2011)
   http://www.iucnredlist.org
2. WWF Hong Kong (June, 2008)
   http://www.wwf.org.hk/eng/maipo/wildlife/invertebrates/midget.php
3. Society for Wildlife and Nature. (2006) Conservationists amazed at endangered damselfly discovery. International Conservation Newsletter, 14(2): 5 - 6.
4. O’Toole, C. (2002) The New Encyclopedia of Insects and their Allies. Oxford University Press, Oxford.
5. Watanabe, M. and Mimura, Y. (2003) Population dynamics of Mortonagrion hirosei (Odonata: Coenagrionidae). International Journal of Odonatology, 6(1): 65 - 78.
6. Moore, N.W. (1997) Dragonflies: Status Survey and Conservation Action Plan. IUCN/SSC Odonata Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.