Blue Skimmer Dragonfly: Orthetrum caledonicum

Blue Skimmer Dragonfly
Orthetrum caledonicum

Location: Western Australia, South West
Season: Summer, December
Order: Odonata 

Suborder: Anisoptera 

Family: Libellulidae 

Genus: Orthetrum 

 Orthetrum caledonicum

Blue Skimmer Dragonfly is commonly found in Australia. It is powder blue in colour, hence the name Sky Blue Dragonfly. The fly's body has a waxy coating and when light passes through the colloidal wax, all light is absorbed but blue light is scattered by the particles, making the insect look blue (Tyndall Effect). The process of colour change is called Pruinescence.

Blue Skimmer Dragonfly with remnants of yellow still on the abdomen undergoing pruinescence

The young males, which are freshly moulted from the larval stages are yellow in colour. This is before they are coated with the waxy substance which results in the blue colour. The colour changes from yellow to blue can be seen in maturing males. Males and females look different. The female is not blue at all, even the mature ones.

In the two photos below, the dragonfly is yellow, which could be a young teneral male or a female. 

Young Teneral Male or Female Blue Skimmer Dragonfly 

Young Teneral Male or Female Blue Skimmer Dragonfly 

When I first saw this yellow dragonfly which is actually a Blue Skimmer, I confused it with the Australian Emerald Dragonfly (and misquoted it on Instagram). The description and pictures in the field guides I read had stark similarities. Two things confirmed for me that these are Blue Skimmers. One, I actually saw the process of Pruinescence as demonstrated in the second photo. Two, I actually spotted an Australian Emerald Dragonfly! Please pardon the quality of the picture below, I must get a good shot next time. But the metallic green coloured markings on the abdomen can be seen. The eyes are bright greenish blue. 

Australian Emerald Dragonfly
Could be a Tau Emerald as T mark is not visible in the photo
Hemicordulia australiae