The following foods listed are not inclusive of all possible foods available for newts' consumption. All foods are subject to availability. Therefore, items such as tubifex worms are not listed due to lack of availability in my area. Without direct knowledge I am unwilling to provide comment.

IMPORTANT NOTE: Caudates main food source is and should be live foods such as those listed below. Remember, newts and salamanders are amphibians, not reptiles nor fish and require certain foods for essential nutrition in their diets. Therefore avoid any variety of fish foods which contain excessive plant material. Lettuce, fruits or vegetables and cooked or raw meats are also unacceptable. Caudates are unable to digest these foods, causing it to lay in their stomachs which can lead to serious stomach ulcers!

TYPES OF FOOD:

Terrestrial species thrive mainly on live foods, whereas aquatic species will consume a broader range of food, including live.

LIVE:

NOTE: Live foods are best purchased commercially or cultured yourself, in order to avoid the possibility of disease.

VITAMIN SUPPLEMENTS:   Strongly suggested in order to boost nutrient content in most live foods, not only crickets. Not required for worms as they are already the most nutritious food for your newts and salamanders to eat. Vitamin supplements are sold in various forms such as powders, sprays and pellets. One such example is the brand Rep-Cal that provides a calcium with vitamin D3 powder as well as a multivitamin powder. Combining the two equally provides an excellent balance! 
 

WORMS:

NIGHTCRAWLERS: An excellent food source as they are high in vitamins and minerals. Commonly found in fishing bait stores. It is suggested to inquire about the origins of the worms. Some smaller operations catch the worms themselves and therefore may have come in contact with pesticides or pollutants. Whereas some businesses purchase their earthworms from suppliers or worm farms which grow their own for distribution. These are safer, as there is no concern about the use of pesticides, and easier than catching your own.

Nightcrawlers should be kept in a fridge or cooler,  45 to 60 degrees, out of sunlight and kept moist, not wet. Be sure to punch small holes in the top of the container for oxygen. When storing unused nightcrawlers for longer than one month, they should be fed in order to maintain vitamin content and of course, to prevent the worms from dying of starvation. However, worms should not be kept longer than a maximum of 6 months at a time in order to maintain freshness and to retain nutrient content as well. Worms kept longer than this period will begin to die and spoil, unless a large and quite deep enclosure can be provided. Depending on the size of enclosure and amount of worms being kept, amounts of food should be varied. However, approximately 4 ounces, which is the equivalent of 1/2 a cup, of chopped produce wastes can be fed every 3 or 4 days, or as consumed. Also, small amounts of corn meal can be sprinkled lightly on the soils surface daily, or as consumed. Do not overfeed or the food can grow moulds. Also remember, do not use any already mouldy foods as this will cause the worms to spoil, thus causing disease. Make sure to cover and bury the food within the soil or it will become mouldy, again possibly causing disease and also annoying fruit flies to form. Avoid using meat products, salt, vinegar, cooking oils and dairy products. Instead organic foods, fruit and vegetables, grass and leaves, coffee grounds, tea bags, citrus peels and crushed egg shells are suitable. Nightcrawlers should be appropriately sized for your newts. Rinse any excess dirt off the worm, and chop into smaller pieces and simply dropped into the habitat or placed on a shallow dish.

EUROPEAN NIGHTCRAWLERS: Similar to nightcrawlers, but slightly smaller in size. See nightcrawlers above for complete information.

My Oregon newt, Chiko consuming a Euro nightcrawler :)

REDWORMS:  Found in compost, these are smaller than nightcrawlers, and useful for adults and juvenille newts. They are very nutritional as well. These can also be purchased at most bait stores to prevent any concern. Redworms can be given whole or chopped into pieces, depending on the size of your newts. The main problem with redworms is that they burrow deep into the substrate, causing the newts difficulty in locating them. One method to prevent this is to purchase a worm feeder cup. These are available in the fish section of most pet stores. Sold for use with fish, but are safe for newts. The plastic cone contains small holes which prevents the scattering of the worms. Held in place with a suction cup, the feeder cup can be lowered to any level, thus providing easier access for the newts. Another option is to handfeed (see Feeding Methods).  For terrestrial specie, worms could also be placed into a shallow, plastic dish or small bowl so long as the newts can see the movement of the worms and can easily access and exit.

Worm feeder cup.

Store in original container at room temperature, refrigeration is not required. If storing for longer periods be sure to keep the soil damp, remove any dead worms and provide small amounts of food as suggested below. You can even start your own compost and grow your own redworms, as they are easily kept and reproduce quickly and effortlessly. Using black earth, place redworms in a plastic container or wooden box lined with newspapers. Be sure to provide small holes in the lid for ventilation, and keep at room temperature. The soil should be kept fairly moist at all times. Provide food such as lettuce leaves, apple peels and pieces of bread for the worms to feed on. An alternate food source are plain, rolled oats. Mix the oats and water in a bowl, refrigerate and pack into a ball. Dig a hole in the soil, place the ball inside and cover. Avoid adding tea bags, coffee grinds, orange peels, or anything containing citrus acid. Cover all food with soil, or any uneaten food more than a few days old, will have to be removed as it will grow a white fuzz over it.

Need to store your worms longer? Having trouble finding worms in the winter months to feed your newts and salamanders? My advice is to stock up in the fall and prepare them to be stored over the winter. Depending on the number of worms needed to be kept to get you through this period, large and deep plastic containers with lid will be needed. Refrigeration will also be required so make room in your fridge or invest in a bar fridge or a portable cooler such as the Koolatron. Worms are best kept at temperatures between 45 and 60 degreesF and out of the sun. Small holes will be needed in the container for oxygen. Substrate can range from soil to shredded newspaper (black and white only as colour ink can be toxic to the worms) to my favourite worm bedding. Frabill Worm Bedding. Sold in the fishing/outdoors dept of local retailer. Versus soil this bedding will keep the worms free of dirt and odours, has a built-in food source and is Ph balanced. Simply add non-chlorinated water to the bedding and transfer the worms. Worm food can be added to the bedding when storing worms longer than a month to increase nutrition and as the built-in food source of the bedding becomes depleted. Replace bedding or soil with new every 8 to 10 weeks. Another food source would be organic foods, fruit and vegetables, grass and leaves as well corn meal and oat flakes can be used. Any substrate should be kept moist, never wet.

Example of worm bedding and food.
 

CRICKETS: An important food source as they can also be high in vitamins and minerals. Most commercially available crickets tend to be less nutritious, therefore gut loading is suggested, see below. It is preferable to feed appropriate sized crickets. Smaller species could choke due to the hard exoskeleton of the large adults. 

When buying more than needed for a single feeding, any extra crickets will need to be placed into a separate container. An extra aquarium, a Critter Keeper available at most pet retailers, or even a simple, plastic Tupperware container will suffice providing the container has a suitable cover/lid to prevent the crickets from escaping. Be sure the cover/lid has a sufficient series of small holes throughout for oxygen, or the crickets will die quickly without adequate ventilation. Be sure to monitor your screen, if used, as crickets tend to eat small holes in the screening material in an effort to free themselves, thus providing generally unseen escape routes for your newts/salamanders! Add sufficient hiding places for the crickets, even sections of egg carton will suffice, as they are cannibalistic. Without this set up, the crickets will die within a few days. It is recommended to periodically wipe the container using damp paper towels in order to remove dead crickets and feces. Best kept in a basement, or cool, damp place. The crickets should be fed in order to maintain some vitamin content and of course to prevent them from dying of starvation. Crickets can be fed on a variety of foods, mainly organic foods, apples, vegetables and mixed greens every 3 to 4 days or as consumed. Cricket food, sold in pellet and powdered forms, can also be purchased at most pet stores. A small, shallow dish of water must be included. Crickets must be able to exit the water easily, as they will drown quickly. This can be prevented by providing a stick(s), or moss into the water dish for the crickets to emerge onto. There are products that can be used in place of water. Gelled products such as Flukers “Cricket Quencher” is one example. Cotton balls can also be used, the idea being that the crickets merely suck on the cotton in order to extract the water.

GUT LOADING CRICKETS:   Term used when referring to adding vitamins to a crickets diet. Although an important food item in newts' diet, most commercially available crickets are low in calcium and high in phosphorous thus gut loading is suggested. Crickets should be fed with this "gut loading" supplement diet for at least 24 hours before being offered. This is easily done by feeding the crickets vegetables and/or mixed greens prepared with the vitamin supplement accordingly. Subsequently, all crickets should be dusted or sprayed before being fed to the newts or salamanders. When dusting the crickets, place a measured amount of powder in a suitable, plastic container or Ziploc bag, and add the crickets. Shake until fully coated. For best results, this procedure should be used at each feeding, and uneaten crickets removed and re-coated before being offered again.

Example of cricket dust.
 

WAXWORMS:  Actually a type of moth caterpillar, not a worm. As with all live foods, again should be appropriately sized for the newts and salamanders. Large waxworms tend to have a harder skin, and may pose a digestive hazard. Waxworms are fat grubs with small heads and soft bodies which makes them easily digestible. A great addition to the main diet, however due to the high fat content should be given sparingly. Waxworms should be stored between 55 to 65 degrees with low humidity in original containers. For longer periods of storage refrigeration is required. Food and water is not required as they live off the fat supplies in their bodies at this stage. Remove any dead black ones. If kept under the right conditions long enough the larvae will cocoon and hatch into tiny moths which, if the newts can catch them, provide an alternate food source.
 

MEALWORMS:  Commonly and improperly sold as maggots. Maggots are completely different from mealworms. Mealworms are the larval stage of a beetle, not a worm. Available in various sizes these can be fed to various species. A great addition to the main diet but again must be appropriately sized. Easy to keep. Store in original container or alternate plastic tub with egg carton for shelter. If storing for months, place in a refrigerator between 45-50 degrees to keep the mealworms in a dormant state. If kept long enough the larvae will turn into pupa and emerge as beetles. These can be used as an alternate food source as well, again size appropriate. To accomplish this simply store mealworms in a medium size, plastic container. No lid is needed as they can’t climb plastic and air is required. Keep the container warm, between 65 and 75 degrees as this speeds the process. Egg carton or layers of newspaper for shelter, rolled oat flakes or vitamin supplements for food and wet cotton balls for water. If you wish to breed the mealworms then do not remove the beetles as they will be needed to mate and lay eggs.
 

MAGGOTS: Fly larvae. Small and appropriate for various species of newts and salamanders.
 

SLUGS: An acceptable food source, however be cautious where pesticides may be a concern. No need to rinse, feed as is.
 

BUTTERWORMS: Fairly new item available at most pet retailers or by special order. Actually a type of moth caterpillar and not a worm. Similar to waxworms but are very expensive, costing as much as $10 a dozen or more. Butterworms are an excellent addition for variety, however should be used as a treat and not part of the main diet. Not only because of the expense but mainly due to the very high calcium content of these worms. Given too often or too many can cause a calcium/vitamin imbalance in the newts’ system over time. On the other hand, a newt which has a calcium deficiency issue, symptoms including uncontrolled muscle twitches, deformed or soft bones or one which is experiencing malnutrition from an illness can be beneficial. Use wisely.
 

HOUSEFLIES AND MOSQUITOES: Wild-caught flies and most especially mosquitoes are not a recommended food source for newts, as they carry the potential for transmitting diseases. Mosquitoes in particular can be very dangerous and should be strictly avoided due to the increase in the West Nile virus!
 

BUGS/INSECTS: Can provide the recommended variety and the essential nutrients found in live foods. However, caution must be used as well. Most insects are not commercially available nor sold through breeders so insects must be collected personally. In order to effectively minimize potential risk of pesticides and pollutants, do not collect bugs within city limits, near chemical or sewage plants, in farmers fields or beside roadways. In order to greatly reduce the risk of contaminants, gather insects within secluded, wooded regions which contain healthy plant and wildlife growth. Using a butterfly net with a fine mesh, sweep through tall grasses and bush. This can yield a variety of insects. Be sure to remove any insects which would be too large for your newt to consume and also any with hard exoskeletons or sharp incisors, which could cause injury and/or digestive trouble. Place insects in a clean jar or plastic container which has a suitable cover/lid with a sufficient series of small holes throughout for oxygen. Insects can also be fed a gut loading diet to enhance vitamin and mineral content. See "Gut Loading Crickets" above. 
 

FLIGHTLESS FRUIT FLIES: Simple and effective food source which is highly nutritious. Although these are quite small in size, they are useful for young as well as adult newts, aquatic or terrestrial. These are commercially bred and can be purchased in the reptile section of most pet stores. Flightless fruit flies can be cultured yourself, and would be quite economical. Personally, I have had no success with any of the medias used thus far. Flies are stored in a plastic vial, and should be kept at room temperature. To use, simply remove the foam plug in order to dispense the flies. To easier control the number of flies released, tap the vial before removing the plug, thus causing the flies to fall to the base. Hold on a slight angle and lightly tap the vial to release the flies.

There are two species of flightless fruit flies: Drosophila Melanogaster and Drosophila Hydei. The Melanogaster species are much smaller in size than the Hydei, and the main disadvantage is that they hop. This makes capturing the small flies considerably more difficult for the newts. Also, the Melanogaster species have a shorter life span, approximately 12 to 15 days, compared to the approximately 25 days of the Hydei.

Common packaging of flightless fruit fly cultures.
 

SNAILS: Another food source, but recommended to be purchased through a breeder, as wild caught snails may carry parasites, which can transmit to the newts. Snails would have to be small in size as the newts would be unable to digest the hard shell of the larger ones.
 

FISH: Small feeder fish, such as guppies, can be purchased at pet stores; convenient, inexpensive, and are readily available. However, even though nutritional, feeder fish are best avoided entirely. A word of caution: Fish can be carriers of bacterial and/or fungal diseases, commonly susceptible to the disease Ick, and therefore would transmit to your newts.

FROZEN:

Commonly used for aquatic specie. Terrestrial specie may or may not eat frozen foods but you could try. Thaw a small portion and feed with plastic tweezers. There are many varieties of frozen foods available from your local pet store. The label on frozen foods should specify "freshwater". Avoid foods which are strictly "saltwater". Freeze-dried foods should be avoided, as this process eliminates some, if not all vitamin and mineral content as well as the moisture content, which is generally what the newts find appealing. Frozen foods are preferred, especially the brand Bio-Pure. These foods are high in vitamin content, are parasite free, and contain no harmful bacteria. Some frozen foods are sold in individualized packages, and others as one solid block. Portions will vary with different factors, so experimenting is best. See "Food Portions" in Feeding for further explanation. Simply break off the appropriate sized portion, drop into the water and after a few moments it will thaw and break up in the water. Using your fingers will allow you to easier disperse the food. Also, briefly unplugging the filtration system will allow the food to settle to the bottom easier, and prevents the food from being caught in the filter or spread throughout the aquarium.

Examples of frozen food varieties.

BEEFHEART: High in fat content, so portions should be kept small and only given occasionally.

MYSIS AND GHOST SHRIMP: Extremely high in nutritional value and completely salt free.

BLOODWORMS: Midge larvae. High nutritional value.

COMMUNITY MENU: A mixed variety consisting of brine shrimp, clam, krill and spirulina.

DISCUS DELIGHT: A mixed variety consisting of turkey heart, brine shrimp, algin and spirulina.

BRINE SHRIMP: Very high in salt content and therefore should be either completely avoided, or given very sparingly, as high salt content is unhealthy to newts.
 

NOTE:  Frozen foods with algin and spirulina added are safe to use. Newts and salamanders naturally consume other animals that would have small amounts of this in their stomachs already from the foods they have consumed. But avoid strict plant material!

COMMERCIALLY PREPARED:

This group consists of flakes and pellet foods, such as trout chow, tropical fish flakes, and food sticks many of which are not appropriate for newts and salamanders. Some may be used for added variety to newts' diet, a treat, providing some of the nutrients needed for good health but is not recommended. Fish flakes of any kind are to be strictly avoided at all times! Newts and salamanders are amphibians and not fish, therefore many fish related foods are best avoided due to possible health risk. Most flakes and other fish related foods are plant material based which means that they can NOT be digested by amphibians and therefore will lay in their stomachs causing serious stomach ulcers and possibility of death!  If using food sticks, such as Tetra ReptoMin newt pellets or Newt and Salamander bites, be sure to break the sticks into small pieces before placing into the aquarium, as they will grow when placed into the water. Many newts will not consume the pellet foods available but again are not recommended anyway. Be advised that not all newts will eat these foods, and regardless, this should not be used as the newts' sole diet. Live foods are essential and will provide plenty of variety and nutrients.

Examples of common pellet foods.