[Syrphidae] Why repeat a genus name as a subgenus?

[Bastiaan]

Hi all,

Can someone explain to me why we use the following form for subgenus as 
if the subgenus is published the same way as published subgenus names. 
(If that makes sence?)

Brachyopa (Brachyopa) ...
Brachyopa (Hammerschmidtia) ...

Lejops (Lejops) ...
Lejops (Anasimyia) ...

Are in the above examples Lejops and Brachyopa a valid subgenus of its 
own parent?
If a subgenus is declared do we use this form so all species of the 
genus are still on an equal level?

Sorry for my ignorance but I am dealing with the relation of names in my 
database for the upcoming new syrphidae.com and I want to do this in the 
currently accepted way.

regards,

Bastiaan