Common Blue Damselfly

Enallagma cyathigerum

Enallagma cyathigerum is a species found mainly between latitudes 40°N and 72°N; It is widely distributed in the Palearctic, common in all European countries and in Asia in Turkey, Iran, Russia, and South Korea, and throughout Ontario in North America. The species reaches a length of 29–36 mm (1.1–1.4 in) with wings 18–20 mm (0.71–0.79 in) long. Damselflies are an important link between the health of the aquatic ecosystem and its response to climate change. The closely related Nearctic species Enallagma annexum was at one time considered to be synonymous with it. Source

Where it is now

In the last 8 weeks this insect was recorded 59 times across 5 areas (each area is a 5 degree square).

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Movement and weather

Each season it is first heard regularly where daytime highs are around 13°C (typically 12 to 17°C, from 7 areas). That holds across 20° of latitude, which suggests its timing follows temperature more than the calendar.

Over the weeks it was present in the past year, its centre in Europe ranged from 47°N in May to 56°N in June, about 1,000 km apart.

Arrival dates

The week it was first heard regularly in each region, after at least six weeks away. Dates differ from south to north, so a region has a range.

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Figures are effort corrected and come from automatic sound identification, which makes mistakes. How this is measured and how it compares with human observers.