|Mating pair of Austrolestes colensonis|
It is New Zealand's largest damselfly, and can change the colour of its body to help thermoregulation. Austrolestes colensonis flies between the months of October to May and is usually seen close to still water, rushes and reeds while the emergence season of the damselfly is highest in January.
Austrolestes colensonis is a member of the zygoptera family, which can be identified by their mobile head and robust multi-faceted compound eyes, short bristle-like antennae, an enlarged thorax supporting the flight muscles for two pairs of richly veined elongated membranous wings and the ten part segmentation of the abdomen. In terms of the species itself, Austrolestes colensonis is the largest damselfly in New Zealand, with an average length of 40 to 47 millimeters. The key identifying features of Austrolestes colensonis are the distinct blue markings on the males and green marking on females as well as the tendency for males to perch at right angles on the support plant. In contrast to the adults, the larvae are between 17 and 21 millimeters in length and characterised by a broad head with large eyes, cylindrical body shape, rounded tip on the tail gill with no hairs and three horizontal brown stripes. The larvae are quite active due to their ability to perform jumping movements and when disturbed the larvae swim very rapidly with the legs held close to the body towards the bottom sediments in which it buries itself. Adult males can be distinguished by their widely separated blue eyes alongside a pale blue upper border on the mouthparts. The thorax has three blue stripes separated by black, which is the predominant colour of the Austrolestes colensonis. Along the abdomen each segment from two to seven has a blue anterior ring located on the margin between segments, the remainder of the abdomen is black except for a dorsal blue area on segment ten. Females have similar characteristics to the male with the exception of having a bright yellow-green colouration, a thicker abdomen and being clubbed distally.
Austrolestes colensonis were observed at two different sites of variant elevations in New Zealand; they were found to have a two-year life cycle. Some eggs hatched directly the summer that they were laid while others overwinter and hatch the following spring. Deacon stated that organisms that form the height of the spring hatch are well developed embryos that can push through the winter in a state of quiescence. Temperature was the major influence that regulated the rate of development; any temperature near or below the threshold inhibited early embryonic development and eventually caused death to the embryo. Eggs can be hatched in about 20–21 days at 20 degrees Celsius, in others the developed embryo forms the overwintering stage. Before emergence, the nymphal darkens until it is near black. Rowe (1987) found that the nymphs may take several short trips from the water a few days before emergence, which takes place on rush stalks 10–40 cm above the water line. It is common for there to be a high rate of mortality due to the moulting adult losing its grip on the substrate and ending up in a body of water where it can drown. Emergence occurs during the day from the months of October to February, with the majority bursting around January but adults can be found at late as May in Dunedin and in early June in Northland. After emergence and maiden flight, young adults mature sexually for several days; during this time there can be quite a high number of dispersals. Once males reach maturity they venture out to find habitats suitable for breeding and to set their territories where they stay motionless on their established porch for extended periods of time until they are bothered by an intruder. Early afternoons, the height of reproductive activity, you will see males go chasing after females that fly through their territory. Rowe (1987) explains that oviposition generally occurs in tandem; the pair land on a floating piece of vegetation and the female drives a shaft through the stem and into the pith. She then lays 6–9 eggs, taking up to a minute. This is repeated and eggs are laid out either in close batches or spaced between one another. Once the nymphs are hatched they begin to search for water so they can moult and release the second larval instar (about 2.3 mm long). These nymphs are quite active swimmers; once they reach a later stage they roam about on the surface of detritus and vegetation on the bottom of ponds.
Diet and foraging
The larvae are cannibalistic and this was shown with fewer than 15% of larvae surveyed had prey in them when dissected. They eat a range of things consisting of Oligochaeta, Rotifera, Cyclopoid Copepoda, Ostracoda, Chydorus sphaericus, Simocephalus vetulus elizabethae, Hydracarina, Sigara spp, Anisops spp, tiny Zygoptera larvae and Chironomidae larvae. They catch other water insects by hiding amongst submerged vegetation then when they come within striking distance they pounce. The larvae also eat each other the bigger, more dominant eat the smaller. It is a process of natural selection where the more dominant and fast survive (Rowe, 1992). The New Zealand damselfly adult eats other bugs around its laying pools and ponds. They mainly feed on other winged bugs usually smaller than them (Johnson, 1991).
Predators, parasites, and diseases
The larvae of the New Zealand damselfly also have predators even though they are usually one of the more dominant species in their pooling area. The predators consist of fish and beetles that they hide from in weed and submerged vegetation. They also are a predator to their own species as mentioned in their diet.
Humans also contribute significantly to New Zealand damselfly survival with their power to redirect streams, leaving dry ponds with larvae unable to survive and eggs unable to hatch. Natural events, such as droughts, can also cause ponds and streams to dry up with similarly deadly results for larvae and eggs.
Austrolestes colensonis or commonly known as the blue damselfly, in Maori is known as Tienieme, which means "to lurch up and down".
Austrolestes colensonis has been found to show aggressive, agonistic behavior. Larvae remain still and sit in one spot for hours and are easily bothered by disturbance. Rowe (1992) observed captured larvae that were placed in aquariums. The larvae were perched on two separate straws, one vertical, the other horizontal; each larvae defended their territory from the other organism. If larvae were put together in high numbers it was noted that they would lose legs or caudal lamellae on occasion in intraspecific interactions. Attacks that would occur sometimes resulted in the severing of a seized appendage, however there were no signs of predation after the event. The larvae executed various forms of postures and motor patterns as observed by Rowe (1992), including:
- Stand Up
- Head Stand
- Head Stand Walking
- Abdomen Bend Down
- Pull Down: When the animal displayed this type of movement others joined in and followed the same behavior.
- Slow Pull Down
- Abdomen Raise
- Slash: Directed away from the invading animal being challenged.
- Lateral Move: A ‘crablike motion’
- Rub Caudal Lamellae
- Rub Rear Tibiae
- Rub Fore Tibiae
- Strike: Austrolestes colensonis struck with their extensible labium-usually aimed at an opponent’s leg
- Staring: 2 larvae stand and face each other for some time.
- Lock On
Austrolestes colensonis also exhibit thermoregulation behavior. There are two mechanisms involved: physiological colour changes and behavioural responses. They change in the intensity of their blue colouration. Males are pale blue-purple earlier on in the morning or after being cool for several hours, as they warm, first the thorax then the abdomen, gain a bright blue colour, in both males and females.
- "Austrolestes colensonis – New Zealand Blue Damselfly". Ray Wilson Bird & Wildlife Photography. Retrieved 2012-03-22.
- Crowe, Andrew (2002). Which New Zealand Insect?. Penguin Books. p. 78. ISBN 0141006366.
- Gullen, P., & Cranston, R. (2005). The Insects: An outline of entomology (3rd ed.). Oxford, England: Blackwell Publishing Limited.
- Rowe, R. (1987). The dragonflies of New Zealand (1st ed.). Auckland, New Zealand: University of Auckland Printing Services.
- Landcare Research. (n.d.). Blue damselfly (Lestidae: Austrolestes). Retrieved from http:// www.landcareresearch.co.nz/resources/identification/animals/freshwater-invertebrates/guide/jointed-legs/insects-and-springtails/dragonflies-and-damselflies/blue-damselfly
- Rowe, R. (1985). Intraspecific interactions of New Zealand damselfly larvae I. Xanthocnemis zealandica, Ischnura aurora, and Austrolestes colensonis (Zygoptera: Coenagrionidae: Lestidae). New Zealand Journal of Zoology, 12(1), 1-15. doi:10.1080/03014223.1985.10428263
- Crumpton, J. (1979). Aspects of the biology of Xanthocnemis zealandica and Austrolestes colensonis (Odonata: Zygoptera) at three ponds in the South Island, New Zealand. New Zealand Journal of Zoology, 6(2), 285-297. doi:10.1080/03014223.1979.10428367
- Deacon, K.J. (1979). The Seasonality of four Odonata species from mid Canterbury, South Island, New Zealand. Unpubl. Ph. D. thesis, University of Canterbury, New Zealand: 209 pp.
- Crumpton, W. J. (1979). Aspects of the biology of Xanthocnemis zealandica and Austrolestes colensonis. New Zealand Journal of Zoology , 285-297.
- Rowe , R. J. (1992). Agonistic behaviour in final-instar larvae of Austrolestes colensonis (Odonata: Lestidae). New Zealand Journal of Zoology , Volume 19 (Issue 1-2), 1-5.
- Encyclopedia of Life: Descriptions and Articles about the Blue Damselfly (Austrolestes colensonis). (2013, January 1). Retrieved March 26, 2015, from http://eol.org/pages/1034261/details.