>>Once they're on veggies, do they really need crickets?
During the first year of life, they really need a diet that is 50-80% insects. A baby beardie goes through a huge amount of growth in the early months and needs that protein. Once they are past the 9-12 month mark, the amount of insects they need in their diet may vary by individual personalities. For the most part an adult bearded dragon can live on a diet that is almost 100% vegetarian like an iguana would as long as the mixture of veggies and greens was a high quality one and supplemented properly.
My youngest dragon, he insists on his 'cricket fix' or he sulks. His parents like a good cricket chase once in a while but seem happy enough if I don't remember to give them any for weeks on end. I have a friend who has had his beardie 10 years now. Back when he got his baby beardie people were just coming around to the idea that beardie diets needed a big overhaul due to short 5-7 year lifespans mainly from obesity in the animals. Back then people would feed adults much like babies - 80% insect 20% veggie and veterinarians were trying to get people to switch the ratios in the other direction and were aiming towards a 50-60% veggie 40-50% insects. I convinced my friend early on to go with that shift some herp vets were pushing once the baby was through the bulk of the 'growth' period where they really needed the high protein of the insects. A couple of years later, I found my friend actually has his dragon on a more extreme shift of 90-95% veggie and 5-10% insect (sometimes he only gets a couple mealworms a week). The animal is alive and doing very well and already showing a nice long lifespan that a beardie is actually capable of.
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PHWyvern