Here is his list of his war service: Cuba, Spanish-American War (wounded in action), Philippine Insurrection, in France, World War I.
The idea is that Hughes won his "Citation Star" for action in Spanish-American War (as well as his retroactive Purple Heart), Citation Stars as you know were upgraded to the Silver Star Medal, here again, I guess at this date he just didn't put in for his yet, perhaps he wasn't aware he was entitled to it yet???.
Here is the list of medals that were authorized for wear of "Citation Stars" as awarded:
Army Regulation 600-40 specified that the "Citation Star" would be worn above a campaign clasp on the suspension ribbon of the medal and to the wearer's right of the bronze service stars on the service ribbon. Authorized Army Citation Stars may be worn on the following service medals:
• World War I Victory Medal
• Civil War Campaign Medal
• Indian Campaign Medal
• Spanish Campaign Medal
• Philippine Campaign Medal
• China Campaign Medal
• Mexican Service Medal
Believe this is the ribbon we're seeing with the Star on it,
There is another medal, but the colors seem different in his photo right.