|Mortonagrion hirosei (Asahina, 1972),
the Four-spot Midget, is a species of damselfly in family Coenagrionidae.
It is found in Hong Kong and Japan and Taiwan-Wugu wetland. Its natural
habitats are rivers and saline marshes. It is threatened by habitat loss.
Length up to 2.5 cm, with four apple-green
spots on its black back, the four-spot midget is a very distinctive and
attractive damselfly`1. 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
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.
Adult four-spot midgets can be seen flying about their habitat from late
May to early August. Like the larvae, the adults are generalized, opportunistic
feeders, which prey on smaller flying insects, such as midges and mosquitoes.
The four-spot midget is a weak flier, and adopts a sit-and-wait tactic
when searching for prey or mates. 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
The majority of the populations are
associated with brackish marshes, but populations have also been found
in coastal freshwater streams. In Hong Kong the adults have been recorded
in mangrove habitat, but the larvae have never been found there. Larvae
of Mortonagrion hirosei have a relatively high survival rate in brackish
water of saline concentrations of up to 15%.
Occurs in Japan, Hong Kong and Taiwan.
It may also exist in mainland China. The species is confined to the coastal
regions of Hong Kong, Taiwan, and the east coast of Honshu, Japan. There
is a single record from an inland site in Gutoushan, Guangdong, China.
The four-spot midget is classified
as Near Threatened (NT) on the IUCN Red List. 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, and suitable habitat in mainland China is similarly being
lost to city development, reclamation and dam construction