Labs often use feed with hormones or other chemicals to aid in their studies. A reliable company will feed high quality rodent feed. The healthier your feeder rodents are, the healthier your snake will be. For insect eaters, you will probably have to feed them yourself for a few days to insure they are as nutritious as possible. Most pet stores and insect suppliers get by with the cheapest feed they can.
For crickets and mealworms, a mixture of cereals, grains, veggies, and some fruit for moisture is a good diet. The more variety you offer the better. Insects like silkworms and wax worms need a special diet. Silkworms need either fresh mulberry leaves, or a special diet which can often be purchased at the same place you buy your silkworms. Wax worms feed on honey in the wild, so you can mix vitamins and minerals into some honey to feed them. Most insectivores also need vitamin supplements in addition to well-fed insects. Shop around and do some research on what brands are good.
Many reptile breeders recommend Miner-all, a mineral-only supplement, and Herptivite’s line of products. Walkabout farm also produces an excellent line of species-specific dusts and insect foods. Whatever you choose, follow the directions on the package. Most supplements can be used at every feeding, but some supplements should be used less often.
Some species of reptiles, especially chameleons, can also be prone to problems related to over-supplementation, so do some research on your reptile’s needs, also.