Hi Alejandro. The smallest known scarab is a termitophile from Cambodia of 1.2 mm. If your measurement is correct, I suspect it to be something else then a scarab, possibly some coprophagous water beetle.
 
Auke

From: Alejandro Lopera <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, 27 June 2013, 4:28
Subject: Dry forest beetle in Colombia

Hi, I'm on a collecting trip in the Colombian dry forest and just collected a small dung beetle, about a millimeter or less, with setae on the elytra. I know it's not much info but its all I can see with my  lens. Any ideas on what it can be? Thanks for the suggestions, cheers

Alejandro