Common Blue and Blue-Tailed Damselflies Compared
A mature male common blue damselfly is blue along much of the abdomen, with black markings on each segment. A mature male blue-tailed damselfly has a mostly black abdomen with one conspicuous blue segment near the tip. That whole-body pattern is the fastest distinction, but females and newly emerged adults need additional characters.
What Does a Common Blue Male Look Like?
Enallagma cyathigerum has a blue thorax with broad shoulder stripes and a blue abdomen marked with black. On abdominal segment two, the black mark is usually rounded or mushroom-like and connects to the dark band at the back of the segment.
The common blue profile places it at many kinds of standing or slow water, often larger ponds and lakes. Mature males may perch low in waterside vegetation or fly over open water.
What Does a Blue-Tailed Male Look Like?
Ischnura elegans is darker overall. The male abdomen is nearly black along most of its length, while segment eight forms a bright blue “tail light.” The colored shoulder stripe is narrower than the broad blue areas on a common blue.
The blue-tailed profile describes a species found across a broad range of waters, including mildly brackish or polluted sites. Tolerance does not mean it occurs in every degraded pool.
How Do You Read the Abdomen?
Count from the segment immediately behind the thorax. Segment two carries useful male markings in many blue damselflies. Segment eight lies close to the tip and is the bright blue section in a male blue-tailed damselfly.
Do not count a narrow dark joint as a whole segment. Take a square dorsal photograph and keep the base and tip in the same focal plane. Side views can hide the upper pattern.
What Do the Females Look Like?
Female common blues may be blue or duller green-brown, with dark torpedo-shaped markings along the abdomen. Female blue-tailed damselflies pass through or retain several color forms, including violet, pinkish, orange, green, brown, and blue.
Color changes with maturity, so a bright orange individual is not automatically a third species. Examine the thorax, abdomen pattern, wing spot, and the shape behind the pronotum. Ask an experienced recorder when those structures are not sharp.
Could It Be an Azure Damselfly?
Yes. A male azure damselfly is blue and black across much of the body and can be confused with common blue. The segment-two mark often resembles a U attached to the rear black band, while the shoulder stripes tend to be narrower. Side markings on the thorax also help.
The azure species profile should be used as a full comparison, not a search for one perfect letter. Natural markings do not always resemble a printed diagram.
Does Habitat Separate Them?
Common blues often occur in numbers around open ponds, lakes, canals, and slow rivers. Blue-tailed damselflies use a wide range of still and slow water and may be common around small disturbed ponds. Both can occupy the same site.
The BDS garden guide notes that common blues tend to favor larger water but can visit garden ponds. Habitat changes probability; it does not override anatomy.
What About Young Adults?
Freshly emerged damselflies are teneral. Their bodies may be pale pink, tan, violet, or weakly marked, and the wings can look glossy. Mature blue coloration develops later.
Record the soft appearance and avoid squeezing the insect for a close look. A teneral can often be narrowed by structure and emergence site, but a confident species label may need to wait for better evidence.
Do Their Flight Seasons Overlap?
Yes. Both can be active across much of the warmer part of the British odonate season, with timing varying by region and weather. Date may rule out an extreme mismatch, but it rarely separates these two on its own.
Record the date anyway. A verified series of observations can show emergence timing, abundance, and range change more reliably than an isolated photograph.
What Should a Useful Photo Show?
- Show the entire upper abdomen from thorax to tip.
- Keep segment two and segments eight through ten sharp.
- Include the shoulder stripes and side of the thorax.
- Record sex only when the body structures support it.
- Add location, date, and water type to the record.
Both species depend on aquatic habitat as nymphs. For that wider context, see where dragonflies and damselflies live.
