|Coenagrion angulatum |
common name Prairie bluet
Prairie ponds and sloughs, slow moving streams.
Adults fly from late May until early August, later in the southern part of its range.
The prairie bluet is more robust and darker blue in colour than the other Eurasian bluets (C. interrogatum and C. resolutum) found in North America (Walker 1953). Males have a distinct colour pattern on the abdomen; segments 3 to 7 are black with blue bands that become progressively smaller towards the end of the abdomen. The end of the abdomen is almost completely blue (Walker 1953, Acorn 2004). Males also have a distinctive black spot on the top of the second abdominal segment and slightly widened terminal abdominal segments (Westfall and May 1996). Female colours are usually yellow-green to tan but can be blue like the males (Westfall and May 1996). Abdominal segments 3 to 7 are dark without coloured rings and segment 8 has pale colouration on top at the base (Walker 1953, Acorn 2004). The dorsal surface immediately behind the head on females has three lobes on the posterior margin; the middle lobe projects above the other two (Walker 1953). Prairie bluets are small damselflies, rarely exceeding 3 cm in length.
Larvae of the prairie bluet are difficult to distinguish from the other Eurasian bluets or even American bluets (genus Enallagma) or forktails (genus Ischnura). The prairie bluet has no obvious characters that allows for identificaion in the field. Coenagrion larvae are of average stature with the posterior margin of the head rounded and eyes not very prominent (Walker 1953).
Sawchyn and Gillott (1975) performed a detailed study on the biology of prairie bluets in Saskatchewan. Females lay soft, creamy-white eggs during June and July in cuts made in living, aquatic plant tissue. Embryonic development takes 2 to 3 weeks. Larvae develop rapidly and near completion by October. Larvae over-winter in one of the final three stages (instars) of development, frozen in the ice that forms in their shallow habitat. The larvae intentionally place themselves where they become embedded in the ice but do not freeze. The larvae remain dormant until April when the ice melts and then continues development. This adaptation likely does not occur throughout the prairies bluets range. Larvae leave the water to become adults by mid-June. Newly emerged adults disperse from the larval habitat to feed and mature. Maturation requires about 1 week and mating occurs away from the water, oviposition occurs within 2 weeks of adult emergence. Oviposition occurs with the male still attached to the female. Eggs are always deposited below the water surface on floating or emergent vegetation. Baker and Clifford (1981) report that taiga bluets can take two years to complete their life cycle; this is likely the case with prairie bluets.
Not currently a concern. Prairie bluets are abundant throughout their range.
Adults feed on flies (e.g. midges) (Sawchyn and Gillott 1975). Larval diet is likely similar to that of the taiga bluet, which feed on, fly larvae, water fleas, other odonate larvae and assorted invertebrates (Baker and Clifford 1981).
Prairie bluets can be found from the western edge of Ontario as far west as northeast British Columbia (e.g. Peace River area). There are records from the southern edge of the Northwest Territories to the north-central states (e.g. Minnesota, South Dakota) (Walker 1953).
|species page author||Jones, B. C.||2005 |