Authors: Theopompos of Chios as cited by Athenaios of Naukratis, Sophists at Dinner 10.443 (link to Greek text and full translation)
Comments: In his work on banqueting, Athenaios of Naukratis (second century CE) pulls together a variety of ethnographic descriptions of meal customs among different peoples (e.g. link for Persians and Medes), including this passage by Theopompos (fourth century BCE) which describes an Illyrian banquet. Despite its brevity, it is worthwhile supplying this passage since there are so few Greek ethnographic descriptions about Illyrians.
The category of “Illyrians” is an outsider (Greek and Roman) term for a variety of peoples who would self–identify more specifically, it should be remembered. So once again this source supplies Greek perceptions of others rather than an historical source for the actual customs of people in a particular place.
Source of the translation: C.B. Gulick, Athenaeus: The Deipnosophists, volume 4, LCL (Cambridge, MA: HUP, 1930), public domain (copyright expired), adapted by Harland.
 In the second book of his History of Philip, Theopompos says that:
“the Illyrians dine and drink seated, and even bring their wives to parties. It is considered good form for the women to pledge any of the guests, no matter who they may be. They conduct their husbands home from drinking-bouts. The men all live a hard life, and when they drink they brace their bellies with wide belts. This they do, at first, with tolerable looseness. But as the drinking becomes more intense, they pull their belts more and more tightly together.”