Its No Picnic The New Tom & Jerry Show : Season 1 Episode 46

Disaster occurs at an insect laboratory when an ant gets a hold of a growing serum. The ant breaks out of the lab and goes on an eating rampage. It runs into Tom and Jerry who are having a pleasant picnic. After panicking they calm down and think of numerous ways to get the ant back to its original size before the ant causes anymore damage to the town.