Common Blue Skimmer (Female)

2. Two yellow stripes at two sides of synthorax; a disconnected yellow spot at the end of the 1st stripe

 

Marsh Skimmer (Female)

2. Synthorax with a brown antehumeral stripe

 

Mangrove Skimmer (Female)

2. More than two thin yellow stripes at two sides of synthorax

 

Lesser Blue Skimmer (Female)

2. Two yellow stripes at two sides of synthorax; a disconnected yellow spot may appear at the end of the 1st stripe