This would be helpful, check out the upper-side of adults and, Identification through larvae is quite easy though. 

You might need to check dorsal side patterns of the imago Pelopidas.

Dear Hareschandra,

I also think this is a Pelopidas agna. As my fellow colleagues pointed out, identification through larvae is easy than trying to identify adult in the field, specially females. However in males, there's a small sex brand on upperside of the forewing. If you draw a imagined line connecting the two discal cell spots (just like Tharaka's drawing here) , it does not intersect the sex brand in P. agna , while this line connecting the two discal cell spots intersects the sex brand towards its middile in P. mathias. 

Best,

Tharindu.

Many thanks for all of you, 

Most of the time for P. agna male space 2 will be narrower and an imaginary line through two radial spots just touch or passing away from the stigma. 4th and 5th istar caterpiller having promiment reddish lateral patch on both of the head.

For P mathias, space in spot two smaller and rectangular. Imaginary line cut the mid or nearer of the stigma. Caterpiller have black patches.