Like other dragonfly species, the white-faced darter has a complex lifecycle which includes a fully aquatic larval stage (2). As larvae or ‘nymphs’, dragonflies are effective sit-and-wait predators with the fascinating feature of being able to fire out the lower portion of the mouth, known as the ‘mask’, in order to grasp passing prey (2) (4). The larval white-faced darter tends to hunt during the day, which makes it particularly vulnerable to predation by fish (3). It is, however, known to grow larger spines as an anti-predator response in the presence of fish (5).
As well as being able to walk, dragonfly larvae are able to move through the water by jet propulsion, expelling water from a specialised rectal chamber in order to propel themselves along (4).
The total length of time spent in the larval stage varies between dragonfly species, with some species spending a few months and others several years as a larva (2). The development of the white-faced darter larva usually takes two years, although some individuals may complete the lifecycle in less than a year (3). The larva undergoes several moults before finally emerging from the water as the readily recognisable adult dragonfly (2) (6). Emergence of the adult white-faced darters begins in early May and usually occurs in the early to mid morning (3). The flying season of the white-faced darter lasts until mid-August and the adults do not over-winter (2) (3).
After emerging, the adult white-faced darter moves to the nearest suitable wood or scrubland, where it will feed and mature (2) (3). The male will then return to near the water, where it establishes a small territory, although this is not aggressively defended (1) (3). The female white-faced darter prefers to bask on open ground and is seldom found near the water (3). Mating takes place in low bushes or heather, and lasts for about half an hour. After this, the female lays the eggs alone, flying low over shallow pools while dropping the eggs onto the waterlogged Sphagnum moss (2) (3).
Dragonflies are skilled aerial predators, usually catching various small insects on the wing (2). The white-faced darter employs a ‘perch-hunting’ strategy, making forays from a perch when prey is sighted, and then returning to the perch in order to consume the prey (2). Generally only active during the day, this species will return to rest in trees and bushes up to 50 metres from the water at night (2) (3).