BruceH's picture

Southern Skimmer

Observed: 1st October 2011 By: BruceHBruceH’s reputation in InvertebratesBruceH’s reputation in InvertebratesBruceH’s reputation in InvertebratesBruceH’s reputation in Invertebrates
Southern Skimmer - Orthetrum brunneum 01-10-2011 16-18-24
Description:
Identifications
Species interactions

No interactions present.

Comments

RoyW's picture

Species correct...

but it's a male! ;o)

BruceH's picture

Gender

I identified it as a female because "Males become totally blue, females are brown overall" (Dijkstra). What are the definitive signs?

Bruce

RoyW's picture

Ooops!

It seems that In didn't take enough time to read the identification before I agreed to it!
I have now removed my agreement and posted a revision.

Male Southern Skimmers go from yellow-brown (similar to females) when immature, to pale blue all over when mature. To me this was obviously a darter, so when I read "Southern" I agreed without checking the rest of the name, or the scientific name!

Darters and Skimmers are actually quie regularly mixed up, particularly when they are immature, as both are bright yellow at this stage, and relatively small dragonflies (in the UK immature Keeled Skimmers are often confused with darters). Many of the diagnostic differences are subtle, but one of the best (if you can get into position to see it) is the number of 'antenodal' veins in the wing (10 or more, with the last one complete in skimmers, 8.5 or less in darters).

The best way to tell the sexes apart is to learn to recognise the shape of the appendages at the end of the abdomen. In all Libellulidae species females have two short, widely separated appendages, while males have two appendages which are very close together. Males also often have their secondary genitailia (under the second abdomenal segment) visible in photos taken from the side.

BruceH's picture

Skimmers and Darters

I should have counted he antenodal veins; I took a number of different photos, and there are clearly 8 veins.

When photographing dragonflies I will try to get shots from below as well, to try to pick out secondary genitalia.