Cockroaches

• Snape keeps a jar of these (dead ones) in his office .
• When Snape catches Harry viewing his Worst Memory in the Pensieve after an Occlumency lesson,  the Professor becomes so angry that a jar of cockroaches explodes as Harry is running away.
• As Harry is riding the Knight Bus from Grimmauld Place to Hogsmeade, someone drops a bag containing frogspawn, cockroaches and custard creams.

Potions Connection

Professor Snape has a jar of dried cockroaches in his office.