■ Frillies eat tremendous amounts of food, especially during their first year of rapid growth. They should be offered food twice daily as youngsters, then daily until adults. You can allow them to eat as much as they want. Adults can be fed about 5 times a week. They are almost exclusively insectivorous. Some will consume vegetable material, so it should be offered for the opportunity.
Roaches make the best staple when it comes to nutrition. They have more protein, less chiton, and are easier to gut-load than crickets. Frilled dragons love them and will often refuse other insects after being fed roaches. Dubia roach colonies are the most popular to maintain for good reasons. They breed moderately fast, have long life spans, and require little maintenance. They also don't climb, don't fly, don't chirp, don't bite, don't smell, and can be housed in a simple rubbermaid bin with egg crates and a small heating pad. A well-started colony will easily be able to accommodate a few hungry dragons. See some of the links at the bottom for info on what to feed them.
Hornworms also make great feeders but are more difficult and expensive to maintain as a staple, and the same goes for butterworms and silkworms. Most will eagerly eat the very nutritious hornworms, these are great as a treat, for anyone in sub-optimal health, and for females during breeding season/gestation.
Superworms & crickets are acceptable. They don't top the good feeder charts, although people do feed them with success. They contain less protein and nutrients than roaches or hornworms.
Mealworms are not an appropriate food source. They contain very little protein and are difficult to digest.
Waxworms should be fed sparingly due to their high fat content. They can be fed as a treat, or to help your frilly gain weight.
Mice can also be fed if they are appropriately sized. Mammals have a better calcium/phosphorous ratio than insects, so they are very nutritional. Pinkies are the smallest size and are good for smaller dragons (they are not overly high in fat and are actually very nutritionally similar to the larger sizes, despite what you may hear). Appropriate sized hoppers and fuzzies can be fed on a somewhat regular basis to adult or sub-adult dragons. Temperatures in the enclosure should be kept high to aid in digestion. Frilled dragons rarely consume mammals in the wild, so rodents may not be an essential part of their diet, however they provide a natural source of vitamin D3 and a high positive Ca:P ratio which can help make up for deficiencies in UVB lighting & calcium supplementation.
Avoid: Mealworms, fish, wild-caught insects potentially exposed to pesticides, wild-caught reptiles, non-whole foods (such as chicken breast).
A well-fed dragon should have a plump round belly, fat deposits on the sides of the tail near the base and on top of the back of the head, robust legs, and barely visible pelvic bones.
In the wild, frilled dragons consume large amounts of termites and ants, and also feed on cicadas, lepidopterans & their larvae, centipedes, spiders, and infrequently small birds, lizards, and mammals.
Raising your own feeders is highly recommended due to the volume the frills will consume on a daily basis. An adult frilled dragon can eat 20-80 crickets a day, 10-20 superworms, or 5-20 dubias. They are their own best judge of how much to eat. It is best to let them have access to as much food as they want. They will stop when they have had enough. Overeating is rarely a concern.
Nutrition & Supplements:
Calcium and vitamin supplements should also be provided. Feeders should be dusted with calcium every day for juveniles, and every other day for adults. This is necessary for healthy bone growth.
The feeders should be gut-loaded because insects are really only as nutritious as what they've been recently eating. Vegetables and fruits will be readily consumed by most insects and will provide vitamins & nutrients as well as water. See the links below for more suggestions.
Many people choose to feed their dragon by hand, or using feeding tongs. Hand-feeding frillies is safe as well. They know the difference between the insect and your fingers. They will also eat out of a dish, and over-eating is rarely a problem. Insects should not be left loose in the enclosure. They will hide well, especially in large enclosures, and much will go to waste. Crickets may also nibble at your dragon, and may be able to chew off toes or parts of the frill while it is sleeping.
Frillies should be offered greens and vegetables on a frequent basis, depending on their interest. Some will eat them, some won't. If they do, it's definitely worth taking advantage of because of the health benefits. For what to offer - the same guidelines as for bearded dragons should be appropriate (Click Here for List). Even if they refuse a "salad", most will eagerly lap up a blenderized mix from a syringe.
→ Important links on raising healthy feeders
Additional reading on roaches, if interested: