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General Summary

"Megalagrion oceanicum" Oceanic Hawaiian damselfly
Conservation status
Critically Endangered (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Odonata
Suborder:	Zygoptera
Family:	Coenagrionidae
Genus:	Megalagrion
Species:	M. oceanicum
Binomial name
Megalagrion oceanicum McLachlan, 1883

The oceanic Hawaiian damselfly (Megalagrion oceanicum) is a species of damselfly in the Coenagrionidae family that is endemic to the island of Oahu, Hawaii. This species is commonly found in the Koolau mountains. This damselfly belongs to the Arthropoda phylum, the Insecta class, the Odonata order, the Zygoptera suborder, and the Megalagrion genus. The oceanic Hawaiian damselfly has a conservation status of critically endangered. It faces several threats like habitat alteration/degradation and nonnative predators.

Description

Oceanic Hawaiian damselflies are large in size. Adults have long, slender bodies that range from 47 to 50 mm (1.8 to 1.9 in)long. They also have narrow, translucent wings with a wingspan range of 51 to 55 mm (2.0 to 2.2 in) . Both males and females have long bodies with black stripes. The males are brighter in color with red stripes, while the female flies have stripes that are pale green. Immature damselflies are also large and have long grasping legs and dagger-like gills. Oceanic Hawaiian damselflies are distinguishable from other species of Hawaiian damselflies by their black stripes and comparatively large size [1].

Life History

During the immature stages of the damselfly, they are aquatic and will feed on small invertebrates or fishes. During the initial stages of development, the damselfly takes up to four months to mature . Once the damselfly enters the adult stage, they emerge from their aquatic habitats and molt into winged adults. In their adult stage, the damselflies will typically stay close to their original aquatic habitats.

Damselfly eggs typically take ten days to hatch. Immature individuals typically take up to four months to mature. There is no known information about the age of sexual maturity, dispersal, or mortality.

During copulation, the female lays eggs while the male protects the female from other rivals by guarding their habitat. They use their terminal abdominal appendages to grasp the female behind the head in order to protect them from rivaling males. This species demonstrates oviposition behavior as the female deposits their eggs . The female will begin the reproductive cycle by laying its eggs in moss, algae, and other submerged aquatic vegetation. Then, in approximately ten days, the eggs will hatch into immature damselflies, otherwise known as naiads [3]. Mature damselflies then crawl out of the water onto vegetation and molt into winged adults. No information is known about the specific timing of reproduction or the quality and quantity of the offspring.

In general, not much information is available on the oceanic Hawaiian damselfly. There is more information on closely related species of damselflies. For example, the annual reproduction of damselflies occurs throughout the late spring or summer. During reproduction, the damselflies are able to produce up to thousands of eggs but have a survival rate of nearly 3% . Overall, more research is needed in regards to details of the oceanic Hawaiian damselfly’s life history.

Ecology

Diet

The oceanic Hawaiian damselflies are predacious species that forage on moss pads and wet rock walls for food. When in adulthood, they feed on small flying insects. While young, they feed on small aquatic invertebrates and fish.

Behavior

During their mating activities, the females lay eggs in aquatic submerged vegetation. They also lay eggs in moss and algae on submerged rocks. While the female lays eggs, the male remains attached to the female, demonstrating territorial behavior. The male clasps his abdomen to the back of the female's head to keep other male rivals with the same characteristics away. In adulthood, the oceanic Hawaiian damselfly flies boldly and strongly . When the species is disturbed, they fly up towards the canopy of the forest over the stream or waterfall they are living in.

Habitat

Oceanic Hawaiian damselflies are found in habitats of fresh running water such as streams and marshes. The young are often found within gravel and moss pads in the swiftly flowing sections of streams. The species stays in the same location year-round, as they are nonmigratory .

Range

Oceanic Hawaiian damselflies are located in Hawaii on the island of Oahu and Ko'olau and Waianae mountain ranges [2]. They are restricted to seven populations in the Ko'olau range.

Conservation

Population size

In 2001, only seven populations of the oceanic Hawaiian damselfly remained in at least sixteen localities on Oahu . During this time, the population size was less than 1,000 damselflies . Currently, there are no updated population sizes for the oceanic Hawaiian damselfly.

Past and Current Geological Distribution

In the past, the damselflies have lived in the Waianae mountain range, located on the western half of the Hawaiian island, Oahu. The species was extirpated, however, from sixteen localities, including the Waianae mountains and leeward streams in Ko'olau. The reasoning for their extirpation is unknown. The oceanic Hawaiian damselfly can currently be found living around the windward sides of the Ko'olau Mountains on the island of Oahu, Hawaii. This species is currently distributed among twelve sites in the Ko'olau mountains .

Major Threats

There are various factors that are impacting this species of damselflies. One factor that is threatening to the damselfly is the increase in urban development and agricultural water diversions because they cause damaging alterations that degrade streams and marsh habitats. Additionally, the prevalence of invasive nonnative predatory species such as insects or fish is a major threat to the damselflies. Similarly, invasive plants threaten the flies as they can alter the damselfly habitat . These threats are very severe because both nonnative predators and plants are very prevalent throughout the limited range of the damselfly.

Listing under the ESA

Megalagrion oceanicum was petitioned for enlistment under the ESA on May 11th, 2004. The species was officially listed as an endangered species on October 18th, 2012.

5-year review

One 5 Year Review was initiated in 2017. This review outlines general updated information about the species and major threats to the damselfly. At the end of the review, it was concluded that no changes to the current listing of endangerment should be made. It also recommends future actions, such as conducting surveys to figure out the distribution of the species, implementing a recovery plan, eliminating or managing nonnative predators, and protecting known habitats.

Species Status Assessment

A species status assessment has not been completed yet for this species.

Recovery Plan

The oceanic Hawaiian damselfly currently has a recovery priority number of 5. A recovery outline for the island of Oahu was published on July 26th, 2018. The plan outlines goals for 27 species on the island, including the damselfly. The major goals of this plan include controlling major threats to the damselfly. This includes habitat loss and predation by introduced species. Targeting these threats will ensure a high chance of species survival for at least 100 years without the need of protection under the ESA. The plan has not been updated.