Feeder Insects

Live insects or other invertebrate prey can be offered as part of a well-rounded diet or given only as an occasional treat for your crested gecko. Properly gut-loaded and dusted with additional vitamins & minerals, bug feeders are a healthy snack!

It is important to remember that unlike leopard geckos, crested geckos are not true insectivores and must consume fruit for a large portion of their diet. This means you can stick to one “staple” insect feeder, with others offered for variety every so often. Preferably, your gecko is eating a suitable powdered diet which contains both the carbohydrates and sugars as well as the fats and protein they need to thrive. Although most crested geckos relish a cricket now and then, some tend to ignore live prey and tend to stress when they are present. You can find a variety of feeders online or at your local pet shops.

With that said, feeding live insects every other week is a good way to offer your crested gecko treats. Some of the benefits of feeder insects are additional protein for growth and they can even improve feeding response overall. It is difficult to say if geckos truly enjoy hunting prey, but it does stimulate the gecko, triggering stalking and pouncing instincts. Reluctant eaters may need repeat exposure to the bug, perhaps enticing them by dunking in wet CGD or hand-feeding.

We’ve been able to get about half of our larger geckos (over 10 grams) to take waxworms and Phoenix worms (soldier fly larva) using tong feeding or simply offering by hand. Smaller geckos seem to prefer actively moving bugs, but persistently offering live foods pays off for most geckos. Some never take to eating bugs.

Before offering feeder insects, you should be sure to provide a nutritious staple MRP that will make up the bulk of their balanced diet. Once the gecko has been established on a proper diet for roughly one month, it is safe to start feeding properly balanced feeders.

Crickets have generally been the insect of choice, but you should not limit your selection to just crickets. Many of the below feeders can be found online, or you can culture them yourself. Just be sure that what you offer is appropriately sized. Too small and it may be ignored, too big and it may be a choking/impaction hazard. Of utmost concern when feeding anything other than a balanced MRP is calcium to phosphorus ratio (Ca:P ratio) in the amount fed. Dusting (see below) will help balance out the insect feeders to make them a healthy and nutritious addition to the crested gecko diet.

Feeder Nutritional Analysis

This list has been compiled from multiple sources, with scientific, zoological and dry matter analysis sources preferred as most credible. Each source varies, and this chart should be considered an estimate as nutritional values vary based on insect diet and husbandry. Most sources do not list dry matter values, which makes it difficult to compare. A good example is the domestic cricket, which contains a lot of moisture but on a dry matter basis is higher in protein than roaches. However, “fresh” feeding should also be considered, and in practice roaches may have more overall nutrition than crickets (due to a larger gut) if properly fed.

Dry Matter vs As Fed

Comparing insect nutrition using DMB, or Dry Matter Basis, allows us to standardize the comparison values of each insect, as some may be “jucier” than others. These numbers may seem higher than other sources, as those likely include moisture in the calculation; adding water back into the analyzed sample will distort the percentages and reflect “as fed” ratios. The dry matter reference is commonly seen in all sorts of animal feed, from dog food to herbivore fodder. If you know the accurate moisture percentage content of the food item, you can convert from “as fed” to dry matter basis, and vice versa.

A cricket is around 70% moisture, so its dry matter content is 30%. Divide the “as fed” percentage of a nutrient by the dry matter percentage. A cricket, as fed, is about 18% protein, so dividing 18% / 30% = 60% protein by dry weight. These numbers are rounded to make an easy example, see the chart below for exact percentages for cricket feeders.

If you want to calculate your dry matter data into “as fed” amounts, you multiply the % of dry matter by the % of a nutrient. If a small Blatta lateralis roach is 20% dry matter and 76% protein by dry weight, you can calculate its “as fed” value by multiplying 20% X 76% = 15% protein as fed. So although by dry matter, the B. lateralis roach has more protein than a cricket, it contains more moisture and that makes their “as fed” protein levels very comparable.

The DMB analysis of these invert feeders includes fat, protein, fiber and ash. Let’s do a little breakdown of what these chemicals mean.

Insect Fat

The fatty acids found in insects are predominantly unsaturated, whereas fats from birds and mammals are the so-called saturated fats. Although no ill-effects (besides necessitating higher basking & night temperatures) in insectivorous/carnivorous species have been reported from feeding foods high in saturated fats in particular, a high-fat diet for most reptiles is as unhealthy as for other animals and can lead to obesity, fatty liver disease, and other complications. Because lipids have more gross energy, 9 kcal per gram vs 4 kcal per gram for both proteins and carbohydrates, fats put on weight faster. Fatty acids are a nutritional requirement, assisting in the absorption of Vitamins A, D, E & K, acting as an energy storehouse, cushioning internal organs and maintaining body temperature. Insects provide a range of fat levels, from 5% to 55%.

The Merck Veterinary Manual recommends linoleic acid (Omega 6) be included in the diet at 0.2%

Deficiencies have not been reported, but reduced stores in the visceral fat have been associated with small clutch size during the breeding season. Atherosclerosis has been reported; restriction of cholesterol may be an important longterm dietary consideration in captive reptiles.

For this reason, it is important to include insects (or supplements) other than roaches to the diet, as the Blattodea order are lacking both linoleic acid and linolenic acid – they cannot synthesize it but it may be added to their diet as a maintenance food or gutload.

Insect Protein

Nutritionally speaking, protein is a chemical compound of amino acids. These amino acids get broken apart from the protein chain so they can then be used for various functions within the body. Essential amino acids are required from foods, while non-essential ones can be bio-synthesized within the body (but also can be used from food). Insects, on a Dry Matter Basis, range from around 40-76% protein. However, each insect species varies and there is also variation among individual insects depending on life stage and diet. Strict carnivores such as cats need at most 32% during critical development, so it is assumed that most (non-toxic, parasite-free) insects should be appropriate for insectivores, for whom we do not have nutritional requirements.

In Douglas Mader’s Reptile Medicine and Surgery, the Nutrition section by Susan Donoghue & Julie Langenberg (151) reports generalized reptile nutrition statistics as follows:
Carnivores should consume 25-60% protein, 30-60% fat and <10% carbohydrate Omnivores should consume 15-40% protein, 5-40% fat and 20-75% carbohydrate Herbivores should consume 15-35% protein, <10% fat, and 55-75% carbohydrate Note that as an insect ages, it generally contains more fat and less protein; the inverse is true for young insects. 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. Strict insectivores, unlike crested geckos, should be fed a variety of insects to make sure they have a complete set of amino acids to work with; however, specific requirements are unknown at this point.

Insect Fiber

Much of an invertebrate’s fiber content comes from chitin as well as cross-linked protein chains from the sclerotization process of the exocuticle. Chitin is a modified composite carbohydrate; most insects don’t incorporate minerals into their chitin matrix, unlike shellfish and other crustaceans. The larvae of soldier flies (Hermetia illucens) does contain significant amounts of calcium in its exoskeleton. Chitin does contain nitrogen which is theorized to artificially inflate protein levels. Regardless, insects are very high in protein when compared to other natural sources. Some insectivores produce chitinase, an enzyme to break down the chitin, but within mammals digestibility ranges from 2-20%, with no data available for insectivorous reptiles, nor is there direct evidence that this digestibility translates into usable protein (nitrogen) from vs carbohydrates.

In terms of dietary ‘‘fiber’’ content, both neutral detergent fiber (NDF) and acid detergent fiber (ADF) content were similar for B. lateralis, averaging about 12% of DM. Approximately 60–90% of ADF in insects is chitin provided by the exoskeleton [Barker et al., 1998; Finke, 2007; Oyarzun et al., 1996]. The ADF content of G. portentosa was 10–13% of DM. However, NDF in this species was considerably higher (36% of DM) and may represent true dietary fiber from vegetables in the digestive tract. Both body and gut content, especially in species with a relatively large gut or consuming high fiber diets, contribute to the nutrient content of feeder prey species. Thus, diet may provide essential nutrients otherwise unavailable from the insect with an empty gut [Finke, 2003; Klasing et al., 2000].

An Investigation Into the Chemical Composition of Alternative Invertebrate Prey by D.G.A.B. Oonincx (Wageningen Institute of Animal Sciences, Animal Nutrition Group, Wageningen University) and E.S. Dierenfeld (Department of Animal Health and Nutrition, Saint Louis Zoo, St. Louis, Missouri). Emphasis mine.

However, when nitrogen from amino acids (not chitin) are reduced from ADF, chitin remains an average of only 3.7% of body nitrogen, depending on species and life stage. Chitin estimates previously reported were above the values found in this method. The hardness of the exoskeleton is due more to sclerotization (the cross-linking of protein chains) than to chitin content; however, this may still inhibit digestibility. The amount of chitin in softer bodied insects is more in line with ADF numbers, whereas the adult mealworm beetle has the largest discrepancy, giving more credence to the theory that protein chains, not chitin, give the insect its hard shell. (Estimate of Chitin in Raw Whole Insects, Mark D. Finke, 2007.)

Insect Ash

In nutritional terms, ash is the “leftovers” when you remove carbon – protein, fat and carbohydrate (fiber). A sample of the food item is decomposed (usually chemically) or treated with high temperatures (ashing), and the remaining “ash” residue is composed of salts, minerals, and metals such as zinc, iron, copper and sometimes lead. Gut contents can also contribute to ash components. It is also possible that ash can contain unbroken chitin compounds, especially with crustacean invertebrates. Feeders have highly variable contents of both macrominerals and microminerals. The calcium to phosphorus ratios (see Dusting Insects, below) are extremely important to the overall health of reptiles. Note that almost all insect feeders are highly skewed towards phosphorus. Other invertebrates, such as annelids (earthworms and other ringed worms) and isopods (crustaceans) contain higher ratios of Calcium to Phosphorus.

For true insectivorous reptiles, you’ll want to provide a high variety of invertebrate prey to ensure appropriate nutrition and novelty in feeding response. For crested geckos being fed a balanced MRP, however, it is less critical.

Feeder Insect Nutrition Chart

Values are by dry weight when possible, resulting in slightly higher percentages than you often see in other food charts, which include water content, lowering the overall protein percentage. Bugs with more moisture (like crickets and wax worms) will have lower percentages.

For a full analysis of insect nutrition, including protein, fat, minerals, vitamins and more, check out our Insect Nutrition PDF.

Item Calcium Phos. Ca:P ratio Protein Fat Source *
———%——— ———%———
Blackworm 0.11 0.85 1:8 47.8 20.1 1
Bloodworm 0.38 0.9 1:3 52.8 9.7 1
Cockroach, American 0.2 0.5 1:2.5 53.9 28.4 1
Corn.borer.larvae, European 0.23 0.64 1:3 60.4 17.2 1
Corn.borer.pupae, European 0.22 0.67 1:3 64.2 17 1
Cricket,domestic 0.14 0.99 1:9 64.9 13.8 1
Cricket,domestic, hi-Ca 0.9 0.92 1:1 65.2 12.6 1
Cricket,domestic, pinhead 0.22 1.27 1:6 * * 1
Earthworm 1.72 0.9 1.5:1 62.2 17.7 1
Fishfly 0.23 1.07 1:5 63.9 19.5 1
Fruitfly 0.1 1.05 1:10 70.1 12.6 1
Fruitfly.larvae 0.59 2.3 1:4 40.3 29.4 1
Fruitfly.pupae 0.77 2.73 1:3.5 52.1 10.5 1
House.fly.larvae, dry 0.41 1.13 1:3 56.8 20 1
Housefly.pupae, dry 0.42 1.18 1:3 58.3 15.8 1
Mealworm.beetle 0.07 0.78 1:11 63.7 18.4 1
Mealworm.pupae 0.08 0.83 1:10 54.6 30.8 1
Mealworm.larvae 0.11 0.77 1:7 52.7 32.8 1
Mealworm.larvae, king 0.16 0.59 1:3.5 45.3 55.1 1
Mealworm.larvae, king, hi-Ca 0.69 0.57 1:1 38.9 45.4 1
Mosquito,adult 0.82 1.24 1:1.5 N/A N/A 1
Mosquito.larvae, dry 0.79 1.07 1:1.5 42.2 16.1 1
Night.crawler 1.52 0.96 1.5:1 60.7 4.4 1
Tubifex.worm 0.19 0.73 1:4 46.1 15.1 1
Water.flea,dry 0.1 1.17 1:12 55.2 6.6 1
Waxmoth.larvae 0.11 0.62 1:6 42.4 46.4 1
Waxmoth.larvae, hi-Ca 0.5 0.33 1:1 * * 1
Butterworm 16.2 5.2 6; 9
Phoenix worm 2.33 1.53 1.5:1 17 10 4; 6
Silkworm 0.21 0.54 1:2.4 64 10.6 5; 6; 7
Superworm 124 2320 1:18 17.4 17.9 6; 8
Hornworm 1:3 9 3 6
Termite 0.26 0.38 1:1.7 42 15 2
* Sources available at https://spreadsheets.google.com/pub?key=0AntsLN7QCkLldDNLM1FLX2xySUtBSEgwaHVXVEJUdWc&hl=en&gid=2

Gutloading & Dusting Insects

Gut-loading an insect refers to feeding the bug a nutritious, well-hydrated food source to ensure proper reptile nutrition. You are what you eat!

Many people are aware of the need to “dust” insects, such as crickets, with calcium powder before feeding them to their insectivorous reptiles. However, there’s more to it than just the amount of calcium; it’s also the ratio of calcium to phosphorus, often referred to as the Ca:P ratio.

Most feeder insects are very high on the phosphorus side. Crickets, for example, are 1:9 calcium to phosphorus without gutloading and dusting. So any time you are feeding undusted crickets you have a bad calcium deficit. Every time any vertebrate animal eats an amount of phosphorus, they need an equal amount of calcium to process that. So a Ca:P level of 2:1 will allow the body to process phosphorus and have some leftover to utilize in bone formation and normal organ functions. Repashy CGD has a 2:1, so by itself it’s perfect, but throw in crickets every week or so it’s NOT enough to keep the calcium from being pulled from their body to process the phosphorus of the insects.

Some people may feel that using Repashy Crested Gecko Diet is adequate to dust their feeder insects. However, dusting with CGD, you are still not fixing the imbalance because it is not designed to “correct” insects. It may slow the deficit slightly, but the more often you feed insects dusted this way, the sooner your gecko will start developing MBD and other calcium deficiency related disorders. Use a product intended for dusting crickets and other insects, like Repashy ICB (now called Calcium Plus) because it is designed to make insects as balanced as possible in all nutrients, not just calcium.

One missed dusting is not bad. Several feedings a month with undusted crickets IS bad.

To balance the nutrition and increase hydration of feeder insects, you should gut-load them with nutritious food scraps or a commercial wet gutload. Dry foods are alright for a maintenance diet (dry gutloads should not be fed long-term), but we prefer to use either fruit, veggies, or gel-based gutloads to properly hydrate our reptiles. Potato peels, sliced oranges, apples and veggie scraps can be used.

Don’t forget to also dust them with a vitamin-mineral powder which contains, at minimum, appropriate levels of calcium and vitamin D3. There are a lot of different dusts on the market, be sure to look for a product that does not contain phosphorous or more than 5,000 IU/kg of Vitamin D3 at each feeding*. This post on Vitamin D3 may be helpful when calculating the amount of dust to use.

* Note that one gram of  vitamin D3 is 40,000,000 International Units (IU), where one IU is equivalent to 0.025 μg (micrograms).

Moon Valley Reptiles recommends the Repashy Superfoods line of supplements. The Calcium Plus ICB (Insect Calcium Balancer), now known as Calcium Plus, is used for dusting crickets or other insect feeders. The RescueCal+ is best for geckos that are starting to have problems from lack of calcium. The SuperCal (NoD) is what you use if you were to leave a dish of calcium out, as it has no vitamin D3 in it. It is not understood whether geckos know how to self-regulate their calcium but this would be the best product to use for a free-feeding dish.

Wild Bugs: Parasites and Chemicals

One reason that capturing wild insect feeders is not recommended is because they may contain parasites, chemical pesticides or other toxic contaminants. Collecting bugs from fields next to highways are also risky because of run-off, herbicides and exhaust. Worms from farms or anywhere near lots of manure are especially likely to carry parasites. Culturing your own feeders and feeding off the second generation helps reduce the risk. This also is useful when seeding your live tanks with isopods and worms, as they may be eaten in the terrarium.

Choosing a Staple Feeder

Crickets are abundant and relatively easy to breed. However, they tend to have a horrific smell if you don’t keep their enclosures clean. They have short lifespans and tend to have die offs that contribute to the smell. They are fast, and they jump. They make a lot of noise. They easily escape. THEY SMELL.

However, they are fairly nutritious (see above chart) and can be a staple feeder for reptiles if you gutload and dust. More importantly, most captive herps as well as arachnids will accept them readily.

Roaches, on the other hand, have several benefits but a few drawbacks as well. Most people do not want to keep roaches in the home, but when properly contained they make a great staple feeder. Choose a non-flying, non-climbing roach such as B. dubia and you will have a quiet, easy to keep, easy to breed, non-escaping food source for your herps. Best of all: they don’t stink. One other drawback besides the “ick” factor of keeping roaches is the fact that some animals, especially those fed exclusively crickets previously, are reluctant to take them.

Be sure to check local laws regarding roaches; Canada and the state of Florida ban the purchase of most roach species, including B. dubia roaches.

Mealworms, superworms are not recommended as a staple for crested geckos because, being frugivores, they may not have the ability to digest high amounts of chitin that are present in these larvae. Other so called “worms” are really grubs, and often contain a lot of fat, such as waxworms, or low in protein (phoenix worm/soldier fly larva) which doesn’t make for a good staple. Crested geckos can be reluctant to take slow moving prey like grubs.

Butterworms have anecdotally been reported to cause problems with crested geckos and other Rhacodactylus species, either by secreting an acidic substance and burning the skin or through secondary parasites. It would be best to avoid them for Rhacs like crested geckos.

Silkworms could be a good staple feeder if your geckos accept them. They are high in protein and low in fat, but are rather large and might be intimidating for small geckos.

All other bugs from the above list would be fine as part of a varied diet. Fireflies or lightning bugs are dangerous! Avoid feeding.

How to Feed Bugs to Reptiles

One of the biggest issues of feeding insects to your geckos or other reptiles is that a well set up enclosure offers numerous hiding spaces to the mobile prey. Crickets can also bite and harass your gecko during the day. You can provide a feeding cup if you pull off the legs of crickets, which is gross. [I have a phobia about insect legs] Some roaches can be fed in a deep votive candle holder or other dish without escaping (make sure they can’t get out before placing in the enclosure). This also avoids impaction risk from a mouthful of substrate when your gecko misses!

Another easy way to feed is to have a spare tub (with lid) or large Kritter Keeper. Place dusted, gutloaded bugs inside, and add your gecko. It may be somewhat stressful for your gecko at first, but place the feeding tub in a dark place for 10 minutes; over time, your gecko should get used to this and will feel comfortable eating. Some crested geckos just aren’t interested in live food, and that is fine. Repashy CGD is complete!

Always chose prey that is small enough to fit down their throat; reptiles bite and gulp, they don’t chew. The general guideline is no wider than the space between the lizard’s eyes. The length should also not be unreasonably large, as with earthworms or other long feeders. To maximize feeding efficiency, it’s better to feed toward the larger end of the safe size limit. Due to their exoskeleton, the more surface area-to-size the less efficient it is to feed several smaller prey than fewer large insects. However, don’t let this discourage you from adding variety to their diet!