When people think about lizards or other non-snake reptiles, they often assume they all eat crickets, the traditional feeder insect. While some lizards are herbivores, most are insectivores. Bearded dragons, leopard geckos, chameleons and water dragons all eat crickets as the majority of their diet or as their sole food source. And a small anole all the way up to the largest monitors (for a while!) will feed on the ubiquitous cricket. Even other “herps” such as frogs, toads, and salamanders (amphibians) and tarantulas and scorpions (arachnids) seem to thrive on crickets.
Should that change?
Well, we shouldn’t abandon the cricket as a staple feeder. Even if today’s cricket is not the same as yesterday’s cricket, they are still a nutritious component of a healthy herp diet. In fact, their movement seems to stimulate a feeding response in most herps, unlike the placid, chubby waxworm. Crickets are high in riboflavin, niacin, and very high in vitamin B12. They are, however, low in thiamin, another B vitamin. The order Orthoptera (crickets and grasshoppers) in general are sources of linoleic acid and linolenic acid – types of Omega 6 and Omega 3 fatty acids. They are high-protein, low fat, and provide reptiles with adequate sources of vitamin E, potassium and iron. They aren’t particularly high in any nutrient that is toxic in excess. For these reasons, and their historical availability and ease of use by the reptile enthusiast, made it the preferred staple feeder.
There are, however, some disadvantages to crickets. If you breed them or keep a constant supply on hand, you already know that crickets are loud and can smell terribly. They also die pretty quickly, which is both wasteful and contributes to the smell! They are known to be opportunistic cannibals. The intensive “farming” of the domestic house cricket, Achetus domesticus, may have contributed to the spread of several cricket virus strains which have wiped out many captive populations in Europe and is now devastating supplies in the United states. So, excluding any nutritional need, you may have to forgo crickets as a staple in favor of a variety of other invertebrate feeders for reasons of convenience, cost, or availability. Many “alternative” feeders, especially roaches, are becoming available online or in locally owned pet stores. You won’t be sacrificing your pet’s health if you give up crickets unless you have a picky eater!
We know very little about the macro- and micro-nutrient requirements of reptiles; we don’t even know how well they digest their prey, especially hard-bodied insects like beetles. We know slightly more about bird nutrition, especially poultry, so a lot of reptile nutritional experiments start with data for poultry, especially with regard to calcium and phosphorus. Unfortunately, most insects are low in calcium compared to phosphorus content, which leads to calcium deficiency if not corrected with a well-balanced insect dust supplement.
High Calcium Insects & Inverts
Even novice reptile keepers should know that insects alone are not enough for their pets because they lack the calcium they need for strong bones and overall good health. This is why a good quality insect dust should be used, with vitamin D3 included – or not – depending on the reptile species, lighting and housing conditions.
Note that most arachnids should not be given dusted insects. They do not have an internal skeleton and excess calcium can cause health problems.
There are some insects and other invertebrates (inverts) that naturally contain more calcium than phosphorus. Phosphorus in the body requires an equal amount of calcium to be processed, so it “sucks up” calcium from either the bloodstream or bones, the body’s calcium storage. Not good! For this reason, you should not use an insect dust that has added phosphorus. It counteracts the calcium and serves no purpose.
Soldier fly grubs, often marketed as Calci-worms or Phoenix worms, are the larval form of Hermetia illucens. They are unique among insects in that they utilize calcium in their chitin matrix – similarly to crustaceans. As such, they do not need to be dusted and may be a candidate for a staple feeder. However, they are lower in protein and higher in fat than crickets, but higher than mealworms which are often used as a staple in the insectivore diet. Little is published about their other vitamin and mineral content, although they do have high amounts of lauric acid, which has some antimicrobial properties.
Soil-dwelling invertebrates like isopods (pill bugs), termites, and earthworms tend to be very high in calcium. Isopods have twelve times the amount of phosphorus, and including them in every 7th feeding has been hypothesized to correct calcium balances naturally. However, it is still a good idea to continue to dust your insects until more data comes forward. Isopods may not be a staple feeder because it is incredibly high in ash. Termites are very nutritious and the soldiers are especially high in calcium. Earthworms may need to be cut to feed to your pet. However, use caution with red wiggler composting worms, as they may be toxic to garter snakes and possibly other herps. Some just won’t eat them because they taste bad. Although these soil-dwellers aren’t common feeders for reptiles, they are used by amphibian keepers, undusted and in conjunction with other live foods, with great success. It may take some time to get your own pet accustomed to eating such novel foods.
High Protein Insects
Protein scores can vary widely among sources, and most use “as fed” basis, which can vary with the size and moisture content of a feeder, along with other factors. Insects, on a Dry Mater Basis (water removed, and insects are more than half water!), range from around 40-76% protein. Even strict carnivores like cats need at most 32% during critical development, so if we use them for a model, all insects will fulfill the dietary need for protein. Young insects usually contain more protein and less fat than adults, except in the case of grubs – the adult form is usually less fatty and contains more protein.
High protein insects (crickets, roaches, silkworms) are a great way to rehabilitate a sick or injured reptile, as the protein is used for cell maintenance and repair. We don’t know the amino acid requirements of reptiles, so feeding a variety is a great way to ensure that your pet is getting complementary proteins (amino acids).
High Fat Insects
Reptiles need fats in their diet just like humans and other animals. However, too much fat can lead to obesity, so you’ll want to make sure your pet isn’t getting too chunky. Waxworms and superworm (Zophobas morio) larvae are especially high in fat, 46% and 51%, respectively. High fat foods tend to also be lower in protein, so you don’t want them as a staple feeder. Mealworm larvae has 53% protein and 33% fat, and that can be used as a baseline for other feeders used routinely.
You may want a high fat feeder if you have an underweight animal, or to keep a female in top condition throughout the breeding season. They are also good occasional treats for herps that are a healthy weight, as they often have higher amounts of fat soluble vitamins and essential fatty acids. Variety is always welcome in a balanced diet!
High Moisture Insects & Inverts
Dehydration can be a killer for reptiles. Stress from captivity, heaters, strong lights in enclosed spaces can lead to chronic dehydration and gout. Gutloading feeders on moist food (fruits, veggies, commercial gels) can help considerably. Earthworms, silkworms, and especially hornworms provide a lot of water and are a healthy addition to the reptile diet. The high moisture content results in lower “as fed” values for some feeders, but it’s good to look at the dry weight values for comparisons.
Feeder Variables to Consider
Just as one insect species varies from another, so do individual insects. Life stage can drastically affect the nutrient content, best seen in the larval stage of flies, beetles and moths. Generally, young insect nymphs have more protein and less fat, as well as higher mineral contents. If a hard exoskeleton is not a concern, it may be wiser to feed multiple small prey instead of one large item.
Feeder diet also plays a role in reptile nutrition, as inverts are often the sole source of food. Vegetables and fruits contain water-soluble vitamins and hydration, while cereals, grains and legumes provide energy and protein for insect growth. Both should be provided to your feeders to make sure your herps are getting the nutrients they need. It has been shown that wild bugs often have more vitamins than cultivated ones, possibly due to varied diet and better overall condition needed to survive in the wild.
So instead of relying on one staple feeder and a little calcium powder, it’s important to research the nutritional value of all the currently available feeders. It’s been our ongoing quest for data here at MVR, combing the internet and published papers for reliable information. There are many myths and rumors regarding what’s best and what’s dangerous, so we want to help out other reptile keepers by collecting and posting what we find. The good news is that most feeders are a healthy food for your reptiles. Many are are available online. Dedicated reptile enthusiasts can already breed these bugs at home, depending on local laws. As demand for variety increases, it should be as easy to provide your herps a smorgasbord of feeders as it is to pick up a bag of crickets at the local pet store.