There are a few oft-touted suggestions as to the difference between a dragonfly and a damselfly. These include:
- dragonflies are larger than damselflies;
- dragonflies sit with wings outstretched whilst damselflies sit with wings held along the abdomen;
- dragonflies eyes meet whereas damselflies eyes are separated.
#1 is simply not so. The largest odonate in the world is a damselfly, Megaloprepus caerulatus (Helicopter Damselfly) with wingspans reaching 19cms/7.5ins. Even just in the UK our Demoiselles, which are damselflies, are larger than our Darters, which are dragonflies. It would be fair to suggest, though, that dragonflies are more sturdily/robustly built. Damselfly abdomens tend to be narrow affairs.
#2 is often true but again there are notable exceptions; the so-called Spreadwing damselflies (Lestidae) usually sit with their wings spread, as does the Odalisque (Epallage fatime) on continental Europe which, I regret, I am yet to see. The so-called Flatwings of Australia are another example.
#3 as stated (simply) is also generally but not always true. Some dragonflies, e.g. Clubtails, have eyes which do not meet, though they are not separated in the same way as those of a damselfly. The head shape of the sub-orders varies markedly and the eye shape differs accordingly. A damselfy head is more dumbell shaped with rather hemispherical eyes whereas a dragonfly has much larger, more wrap-around eyes on a more spherical head.
The technical difference is explicitely stated by the scientific names of the two sub-orders, at least, if you speak Greek, it is:
- means unequal or dissimilar wings – a dragonfly’s hind-wing is broader than the fore-wing.
- means equal or similar wings – a damselfly’s fore and hind-wings are the same shape.