Enallagma aspersum

Azure Bluet


Enallagma aspersum, Azure Bluet lateral image

Family: Coenagrionidae

Length: 27 - 34 mm

 

To beginning Damselfly watchers, all the bluets may seem to look alike. The Azure Bluets, though, have clear distinguishing characteristics that enable one to be confident of a correct identification.

One males, look for an abdomen that has the rearmost segment (S10) black on the top and blue on the sides, while segments 8 and 9 are blue on the tops and sides. Segment 7 is blue toward the rear and black toward the front, with a characteristic pattern where the two colors meet. Male Azure Bluets have very large blue eyespots.

Azure bluet head, eyespots

Female Azure Bluets look not unlike the males at first glance, but each of the identifying characteristics mentioned for the males is different on the females. On females, the final two segments of the abdomen (S9 and S10) are black on the tops and sides. Segment 8 has a pair of small blue spots, and segment 7 has a pair of larger blue spots. The photo at the bottom of this page shows the characteristic size and shape of these two pairs of spots. Another thing to notice about female Azure Bluets is that their eyespots are often greenish, and noticeably smaller than those of the male.

Azure Bluets are found in most of the Eastern United States and into Canada. Look for them at ponds and other small bodies of water. In most cases, if fish are present in a pond, then Azure Bluets are not.

Ingram and Jenner (1976) studied the life history of Enallagma aspersum in the highlands of western North Carolina. They reported that the species spends the winter in the larval stage, in instars F-8 to F-1. Adult emergence was "temporally dispersed." The first emergence was seen on 21 May and the last on 15 September, and there was a brief period in early August where emergence seemed to cease temporarily. The peak of the emergence period was from 29 June to 19 July.

Ingram and Jenner argued that while most Enallagma aspersum overwintered as larvae, about 8% of individuals completed all development in one season, emerging as adults in August and September.

 

Enallagma aspersum, dorsal image

On the abdomen of males, S10 is black on top, while S8 and S9 are blue.

S7 is partly blue, and has a characteristic pattern where the blue gives way to black.

Enallagma aspersum, Azure Bluet photo

 

Right: Female Azure Bluets are black at the tip of their abdomens. They have two pairs of blue spots, one on segment 8 and one on segment 7. The size and shape of these spots is characteristic of females of this species. Note that on females the eyespots are smaller and are often greenish rather than blue.

Note that this female Enallagma aspersum has mites attached to her in the area where the thorax meets the abdomen.

Enallagma aspersum pair in mating wheel