What are Dragonflies and Damselflies?

Dragonflies and damselflies belong to the group (or Order) of insects known as Odonata, a primitive and successful group that emerged more than 300 million years ago. They are found on every continent except Antarctica.

In common with other insects, they are invertebrates with three pairs of segmented legs, a body that is divided into three distinct sections: the head, thorax, and abdomen, with a pair of compound eyes and a pair of antennae.

Today there are more than 5,500 species of Odonata, divided into two distinct groups or sub-orders: Anisoptera (true dragonflies) and Zygoptera (damselflies). There are slightly more dragonfly species than damselflies.

In the UK, the term ‘Dragonflies’ is often applied to the entire insect order Odonata, including damselflies. This makes the distinction between true (Anisopteran) dragonflies and damselflies difficult at times! Some suggest that Anisopteran dragonflies could be called Warrior flies, perhaps in time that will catch on. To help avoid this confusion I generally refer to Anisopteran dragonflies as dragonflies, and the whole order as Odonata.

All Odonata have the following distinctive features in common:

  • The abdomen is long and divided into ten segments.
  • Two pairs of large wings that are able to move independently of each other.
  • Two large compound eyes providing almost 360° stereo vision, and three specialised eyes.
  • Small, inconspicuous antennae.
  • A unique method of reproduction.
  • A two-stage life cycle – their life begins as aquatic larvae until they are ready to emerge from the water and enter the second phase of the their adult life as flying insects.
  • They are carnivores and fierce predators of other insects, including other Odonata.
Odonata, and dragonflies in particular, are superlative fliers and able to fly seemingly indefinitely (they do land though!), they can hover, fly forward, backwards and sideways and change direction endlessly as they chase prey at great speed or seek a mate.

Differences between dragonflies and damselflies

Dragonflies and damselflies are closely related so what separates them?

  • Generally, dragonflies are powerful fliers and tend to be larger and more robust than damselflies. Damselflies in contrast have a weaker, fluttering flight, and much more delicate bodies.
  • In dragonflies, the eyes are very large, and in most species meet at the top of the head. Damselflies in contrast have smaller eyes that are separated on either side of the head.
  • Dragonflies have dissimilar sized pairs of wings; the rear wings are broader – Anisoptera means ‘unequal wings’.
  • Damselflies have similarly sized pairs of wings – Zygoptera means ‘equal wings’.
  • Though not an absolute rule, dragonflies tend to rest with their wings held open and damselflies with their wings closed
Blue-tailed Damselfly - Ischnura elegans. Immature male, River Great Ouse at Roxton.
Blue-tailed damselfly – Ischnura elegans is a typical blue damselfly, common in Bedfordshire.
Broad-bodied Chaser - Libellula depressa. Male, Marston Thrift.
Broad-bodied Chaser - Libellua depressa is a typical dragonfly, and often seen around new ponds.

Why are dragonflies and damselflies important?

Odonata aren’t especially economically important to man, but in some cultures they are used for medicinal purposes, and they can be a snack or a delicacy at the dinner table. But while there isn’t large scale exploitation, they are very useful as ecological indicators.

Most dragonflies and damselflies require clean unpolluted waters for their larva to develop. The presence of larvae and adults is usually a good indicator of water quality, and also that the surrounding environment supports a variety of life on which adults can feed.

While dragonflies can be abundant in some environments, they are susceptible to pollution and habitat (mis)management.  This is especially true when they have specialised habitat requirements, following  accidental pollution of their only breeding site during the 1960s, the Norfolk Damselfly became extinct in the UK. In Bedfordshire the Scarce Blue-tailed Damselfly became extinct with the loss of its last breeding ground at Sundon Chalk Quarry.

Of the thousands of species worldwide only 45 or so are common to the British Isles and 24 of these can be found in Bedfordshire.

Climate change is likely to effect Odonata distribution and over the last 20 years more species are visiting and establishing breeding colonies, both in the UK and Bedfordshire. We also attract migrants and vagrants from time to time, and new species may turn up. Whether these movements are long term range expansions or not remains to be seen, and the world of dragonflies and damselflies is constantly changing.