Butter worms are extremely high in calcium ... more than twice that of most other feeder insects (except for Phoenix Worms in their mature phase - just before they reach the pupa stage). Butter worms are an absolute favorite of most lizards. They are a good live feeder insect addition for added variety in your exotic's diet. Note: Butterworms are high in fat content and should only be given as a treat, not used as a every day staple feeder. Butterworms can be stored for up to 4 months in a refrigerator. and require no maintenance, nor need any feeding or any special care whatsoever, making them one of the easiest live feeders to keep and feed to your pets.