Organic Value Recovery Solutions LLC © Organic Value Recovery Solutions 2010 © Organic Value Recovery Solutions 2010 Encyclopedia of Entomology Springer 2004 10.1007/0-306-48380-7_2920 Nutrient Content of Insects Mark D. Finke¹ (1) Scottsdale, Arizona, USA Without Abstract Insects are an important food source for both animals and humans, and for that reason, reports of their nutrient composition are found in articles in disciplines ranging from anthropology to zoology. One of the first applications of the nutrient content of insects involves their use as food for humans. Evidence from archeological sites suggests the use of tools by early hominids to dig termites from their mounds. The anthropological literature shows that insects have been, and continue to this day to be, an important human food source. While insects are not routinely eaten in most western societies, in many other cultures, insects continue to be an important source of nutrients. As such, nutritional analysis is commonly performed on insects as a means of helping determine the nutrient intake of certain populations. While a variety of species are commonly eaten, the insects most frequently analyzed include lepidopteran larvae (mostly members of the family Saturniidae), coleopteran larvae, a number of different species of grasshoppers and locusts, and several species of termites. The insects most widely consumed by humans are the larvae from three species of palm weevils (Curculionidae: Rhynchophorus). Indigenous people in Africa, South America, Southeast Asia and New Guinea have all developed techniques for mass-producing these larvae, which involves cutting down select species of palms and returning 6 to 10 weeks later to harvest the larvae from the fallen trees. While insects are sometimes eaten raw, in most cases, insects consumed by humans are processed usually by drying, boiling, frying, or roasting. Starting in the 1970s, the nutritional value of a number of insect species have been evaluated as potential foodstuff for poultry, or other food-producing animals. Extensive analyses, including feeding trials with rats, poultry and fish, have been published using house fly larvae Musca domestica (L.) silkworm pupae Bombyx mori (L.) and Mormon crickets, Anabrus simplex Haldeman. In these studies, the nutritional value of dried insect meals have been evaluated when they were fed as the primary or sole source of dietary protein. These data are especially important as they represent evaluations of insect protein quality based on both amino acid analysis and animal feeding trials. Most of these data have been published in the nutrition and animal science journals. The large number of insect species and the diversity of the environments they inhabit also means they are an important food source for many terrestrial and aquatic animals. For that reason, the zoological literature contains articles with nutrient analysis of fresh insects to help evaluate the nutrient intake of wild animals. Termites are the insects most frequently studied in this regard, presumably because they are the primary food source for a number of highly specialized mammalian insectivores. The nutritional content of selected species of cultured insects have also been studied because of their use as food for captive insectivorous reptiles, birds and mammals kept in zoos. The insect species most commonly utilized for these purposes include the house cricket, Acheta domesticus, waxworms (larvae of the wax moth Galleria mellonella (L.)) and the larvae from two species of beetles in the family Tenebrionidae: yellow mealworm, Tenebrio molitor (L.), and superworm Zophobas morio (F.). These analyses are usually performed on raw, whole insects. In an effort to improve the nutrient composition of insects raised as food for zoo animals, the effect of the residual food in the insect's gastrointestinal tract has also been studied. This food can have a substantial impact on the nutrient composition of the insect. For example, the calcium content of fasted house cricket nymphs is about 1,200 mg/kg dry matter, which can be increased to as much as 18,200 mg/kg dry matter when they are fed a high calcium diet. There are a number of issues to consider in a review of the literature on the subject of insect nutrient composition. The first is combining all the information across a wide range of disciplines. A second issue is that insect nutrient composition is sometimes reported on an as is basis, while other studies report values on a dry weight basis, while amino acids are commonly reported in milligrams of amino acids per gram of protein. Another factor to consider when evaluating insect nutrient composition is the effect of handling, preparing and processing of the insects prior to analysis. Insects prepared for human consumption often have various parts removed, most commonly the wings and the gastrointestinal contents, so results may not be representative of the whole insect. Additionally, insects consumed by humans are often processed in some fashion prior to consumption. Processing methods commonly used include drying, roasting, frying, salting and canning, all of which can have substantial impacts on nutrient composition. Lastly, when evaluating the nutrient composition of raw whole insects, the effect of any residual food in the insect's gastrointestinal tract must be considered. In order to help facilitate comparisons between different studies, all the data (except moisture) in the tables have been recalculated from the original data to express the information on a dry weight basis. For all tables, a blank indicates the sample was not analyzed for the particular nutrient. If available, information on how the sample was prepared or processed prior to analysis is shown. The information presented does not represent a systematic analysis of insects, but is simply a collection of data available from the literature. As such, it does not adequately represent data for all families, or even different life stages within a single species, so generalizations from these data concerning the nutrient composition of a family or order is unwarranted. Analysis of insects for moisture, protein, fat, ash and fiber is presented. As expected, raw, whole insects generally contain 55 to 85% moisture. Whole insects with a low moisture content are generally those that also have a high fat content. As expected, insects processed for human consumption generally contain less moisture than raw insects because processing usually involves some type of drying to prolong shelf life. On a dry weight basis, the nutrient in highest concentration is usually protein, which is not surprising given the protein-rich exoskeleton of insects. Protein contents for raw, whole insects range from 21% for the passalid Oileus rimator Traqui larvae, to 80% for adult female gypsy moths, Lymantria dispar (L.). Insects processed for human consumption may exhibit an even wider range as the removal of specific parts will affect the overall nutrient composition. For example, the hairs or setae commonly found on many species of lepidopteran larvae, which would be extremely high in protein, are usually removed when the insect is prepared for human consumption. Fat is the other major component of most insects with raw, whole insects ranging from a low of 2.2% for Nasuititermes corniger (Motschulsky) worker termites, to a high of 60% for greater wax moth, Galleria mellonella  (L.) larvae. Processing of insects for consumption by humans can dramatically affect reported fat contents in two ways. Roasting can remove fat from the insect, thereby decreasing the fat content versus that seen in the raw insect, while frying can increase the insect's fat content. Although there is limited data available, in general, female insects contain more fat than male insects. Data from various species of Lepidoptera suggests that larvae fed artificial diets are higher in fat than those fed fresh plant material. For larvae of the stored product pest, the yellow mealworm, Tenebrio molitor (Linnaeus), providing supplemental moisture increased pre-pupal fat content. Moisture, protein, fat, fiber and ash content of selected insect species.   Method of preparation Moisture (%) Crude protein¹ (%) Crude fat (%) Fiber (%) Ash (%) All values (except moisture) on dry weight basis. ¹ Crude protein measured as nitrogen×6.25 ^aFiber measured as acid detergent fiber ^bFiber measured as crude fiber Lepidoptera             Agrotis infusa (larva) Roasted 49.2 52.7 39.0   5.3 Anaphe panda (larva) Intestinal contents and hairs removed 73.9 45.6 35.0 6.5^b 3.7 Anaphe venata (larva) Dried (without hairs) 6.6 60.0 23.2   3.2 Ascalapha odorata (larva) Whole raw, not fasted   56.0 15.0 12.0^b 6.0 Bombyx mori (larva fed artificial diet) Whole raw, not fasted 82.7 53.8 8.1 6.4^a 6.4 Bombyx mori (larva fed mulberry leaves) Whole raw, not fasted 76.3 64.7 20.8     Bombyx mori (larva fed mulberry leaves) Whole raw, intestinal contents removed 69.9 62.7 14.2     Bombyx mori (pupa) Whole raw (dried?) 18.9 60.0 37.1   10.6 Callosamia promethea (larva) Whole raw, freeze-dried 4.5 51.7 10.5 11.3^b 7.2 Catasticta teutila (larva) Whole raw, not fasted   60.0 19.0 7.0^b 7.0 Conimbrasia belina (larva) Intestinal contents removed then dried   62.0 16.0 11.4^b 7.6 Galleria mellonella (larva) Whole raw, fasted 58.5 34.0 60.0 8.1^a 1.4 Heliothis zea (larva fed broad-beans) Whole raw, fasted 77.4   18.2     Heliothis zea (larva fed artificial diet) Whole raw, fasted 77.5   30.2     Hyalophora cecropia (larva) Whole raw, freeze-dried 2.6 56.2 10.5 15.1^b 6.1 Imbrasia epimethea (larva) Smoked and dried 7.0 62.5 13.3   4.0 Imbrasia ertli (larva) Viscera removed then boiled or roasted, dried and salted 9.0 52.9 12.2   15.8 Imbrasia truncata (larva) Smoked and dried 7.3 64.7 16.4   4.0 Manduca sexta (larva fed artificial diet) Whole raw, freeze-dried 4.7 61.0 21.7 9.9^b 7.8 Manduca sexta (larva fed fresh plant material) Whole raw, freeze-dried 4.7 60.7 17.3 8.8 ^b 8.5 Nudaurelia oyemensis (larva) Smoked and dried 7.0 61.1 12.2   3.8 Porthetria dispar (adult with eggs) Whole raw, not fasted 68.6 80.0 44.6   8.0 Pseudaletia unipuncta (larva) Whole raw, freeze-dried 2.0 55.5 15.2 5.1^b 7.0 Spodoptera eridania (larva) Whole raw, freeze-dried 4.5 57.3 14.6 7.4^b 10.3 Spodoptera frugiperda (larva fed artificial diet) Whole raw, freeze-dried 2.1 59.0 20.6 6.8^b 5.7 Spodoptera frugiperda (larva fed fresh plant material) Whole raw, freeze-dried 3.6 59.3 11.7 12.4^b 11.6 Usta terpsichore (larva) Viscera removed then boiled or roasted, dried and salted 9.2 48.6 9.5   13.0 Xyleutes redtembacheri (larva) Whole raw, not fasted   43.0 48.0 6.0^b 2.0 Coleoptera             Aplagiognathus spinosus (larva) Whole raw, not fasted   26.0 36.0 15.0^b 3.0 Callipogon barbatus (larva) Whole raw, not fasted   41.0 34.0 23.0^b 2.0 Oileus rimator (larva) Whole raw, not fasted   21.0 47.0 13.0^b 2.0 Passalus punctiger (larva) Whole raw, not fasted   26.0 44.0 15.0^b 3.0 Rhyncophorus ferrugineus (larva) Not reported 70.5 20.7 44.4     Rhyncophorus palmarum (larva) Whole raw, not fasted 71.7 25.8 38.5   2.1 Rhyncophorus phoenicis (larva) Incised, fried in oil 10.8 22.8 46.8   2.7 Scyphophorus acupunctatus (larva) Whole raw, not fasted   36.0 52.0 6.0^b 1.0 Tenebrio molitor (adult) Whole raw, fasted 63.7 65.3 14.9 20.4^a 3.3 Tenebrio molitor (larva) Whole raw, fasted 61.9 49.1 35.0 6.6^a 2.4 Zophobas morio (larva) Whole raw, fasted 57.9 46.8 42.0 6.3^a 2.4 Orthoptera             Acheta domesticus (adult) Whole raw, fasted 69.2 66.6 22.1 10.2^a 3.6 Acheta domesticus (nymph) Whole raw, fasted 77.1 67.2 14.4 9.6^a 4.8 Blatella germanica (not specified) Whole raw, not fasted 71.2 78.8 20.0   4.3 Brachytrupes sp. Fresh, blanched, inedible parts removed 73.3 47.9 21.3 13.5^b 9.4 Crytacanthacris tatarica Fresh, blanched, inedible parts removed 76.7 61.4 14.2 17.2^b 4.7 Gryllotalpa africana Fresh, blanched, inedible parts removed 71.2 53.5 21.9 9.7^b 9.4 Oxya verox Whole raw, dried 29.8 64.2 2.4   3.4 Oxya yezoensis Whole raw, not fasted 65.9 74.7 5.7   6.5 Sphenarium histro (nymphs & adults) Whole raw, not fasted   77.0 4.0 12.0^b 2.0 Zonocerus sp. Whole raw, not fasted 62.7 71.8 10.2 6.4^b 3.2 Isoptera             Cortaritermes silvestri (worker) Whole raw, not fasted 77.8 48.6 6.9   8.5 Macrotermes bellicosus (alate) Dewinged, raw 6.0 34.8 46.1   10.2 Macrotermes subhyalinus (alate) Dewinged, fried in oil 0.9 38.8 46.5   6.6 Nasutitermes corniger (soldier) Whole raw, not fasted 69.6 58.0 11.2 34.8^a 3.7 Nasutitermes corniger (worker) Whole raw, not fasted 75.3 66.7 2.2 27.1^a 4.6 Procornitermes araujoi (worker) Whole raw, not fasted 78.1 33.9 16.1   3.5 Syntermes ditus (worker) Whole raw, not fasted 79.7 43.2 3.4   17.1 Hymenoptera             Aphis melifera (adult female) Whole raw, not fasted 65.7 60.0 10.6   17.4 Aphis melifera (adult male) Whole raw, not fasted 72.4 64.4 10.5   17.8 Aphis melifera (larva) Whole raw, not fasted 76.8 40.5 20.3 1.3^a 3.4 Atta mexicana (reproductive adult) Whole raw, not fasted   46.0 39.0 11.0^b 4.0 Oecophylla smaragdina Fresh, blanched inedible parts removed 74.0 53.5 13.5 6.9^b 6.5 Oecophylla virescens Inedible parts removed 78.3 41.0 26.7   6.0 Polybia sp. (adult) Whole raw, not fasted   63.0 13.0 15.0^b 6.0 Diptera             Copestylum ann & haggi (larva) Whole raw, not fasted   37.0 31.0 15.0^b 8.0 Drosophila melanagaster (adult) Whole raw, not fasted 67.1 56.3 17.9   5.2 Hermetia illucens (larva) Dried, ground, not fasted 3.8 47.0 32.6 6.7^b 8.6 Musca autumnalis (pupa) Dried, ground, not fasted   51.7 11.4   28.9 Musca domestica (pupa) Dried, ground, not fasted   61.4 9.3   11.9 Hemiptera             Acantocephala declivis (nymphs & adults) Whole raw, not fasted   35.0 45.0 18.0^b 1.0 Edessa petersii (nymphs & adults) Whole raw, not fasted   37.0 42.0 18.0^b 2.0 Euchistus egglestoni (nymphs & adults) Whole raw, not fasted   35.0 45.0 19.0^b 1.0 Pachilis gigas (nymphs & adults) Whole raw, not fasted   64.0 22.5 7.5^b 3.5 Hoplophorion monograma (nymphs & adults) Whole raw, not fasted   64.0 14.0 18.0^b 3.0 Umbonia reclinata (nymphs & adults) Whole raw, not fasted   29.0 33.0 13.0^b 11.0 As expected, most insects contain only small amounts of ash because they lack the internal calcified skeleton found in most vertebrates. An exception is the puparia of the face fly, Musca autumnalis DeGeer. Unlike most insect species where the cuticle consists largely of sclerotized protein, the puparia of the face fly is calcified and so contains 63% ash on a dry weight basis versus 3.7% ash for the puparia of the house fly, Musca domestica (L.). It is frequently reported that soft-bodied insects contain less fiber than those with a hard exoskeleton, but the limited data available and the use of several different techniques to measure fiber prevents a critical evaluation of this assumption. Additionally, the contribution of the gastrointestinal contents can have a marked effect and is likely the reason for the high fiber values seen for many of the insect species. Looking at the data for Tenebrio molitor, it does appear that the soft bodied larva has less fiber than the heavily sclerotized adult beetle. The structural similarity between chitin (N-acetyl-D-glucoamine linked by β-1-4 bonds) and cellulose (β-D-glucopyranose linked by β-1-4 bonds) is the reason it is often assumed that the fiber measured in insects consists solely of chitin. Given the physical characteristics of sclerotized proteins and the fact that amino acids have been detected in the acid detergent fiber residue, it seems likely that the fiber (measured as either crude fiber or acid detergent fiber) in fasted insects represents both chitin and sclerotized protein. As expected, insects contain little calcium and high levels of phosphorus. While most wild-caught insects also appear to be low in calcium, in general, the values are somewhat higher than those reported for captive-raised insects. High calcium levels have been reported in only a few species of insects. Insects that have been shown to contain substantial quantities of calcium include stoneflies (1.15% dry matter basis), housefly pupa, Musca domestica (0.93% dry matter basis), from larvae raised in poultry manure containing 5.1% calcium, and the previously mentioned Musca autumnalis puparia. Presumably, wild living animals feeding primarily on insects obtain sufficient calcium by varying the prey species consumed, eating insects which have consumed a high-calcium diet and by ingesting soil particles adhering to the prey animals. Lastly, the calcium content of wax worms (Galleria mellonella larvae), house crickets (Acheta domesticus), mealworms (Tenebrio molitor larvae) and silkworms (Bombyx mori larvae) can all be increased 5 to 20-fold when fed a high calcium diet. This increase in calcium appears to be solely due to the residual food in the gastrointestinal tract with little of the calcium being incorporated into the insect's body. Mineral content of selected insect species.   Ca (mg/kg) P (mg/kg) Mg (mg/kg) K (mg/kg) Na (mg/kg) Cl (mg/kg) Fe (mg/kg) Zn (mg/kg) Cu (mg/kg) Mn (mg/kg) Se (mg/kg) Lepidoptera                       Anaphe venata (larva) 400 7300 500 11500 300   100 100 10 400   Bombyx mori (larva fed artificial diet) 1020 13700 2880 18270 2750 3580 95 178 21 25 0.8 Bombyx mori (pupa) 1950 5840 2550       320 284 2 9   Conimbrasia belina (larva) 1740 5430 1600 10240 10320   310 140 9 39   Galleria mellonella (larva) 590 4700 760 5320 400 1540 50 61 9 3 0.3 Imbrasia epimethea (larva) 2250 6660 4020 12580 750   130 111 12 58   Imbrasia ertli (larva) 550 6000 2540 12030 24170   21   15 34   Imbrasia truncata (larva) 1320 8420 1920 13490 1830   87 111 14 32   Nudaurelia oyemensis (larva) 1490 8710 2660 11070 1400   97 102 12 55   Usta terpsichore (larva) 3910 7650 590 32580 33380   390 253 26 67   Coleoptera                       Phyllophaga rugosa (adult) 430   1900 11510 790   170         Rhyncophorus ferrugineus (larva) 15630           146         Rhyncophorus palmarum (larva) 1000 4800 3100 6800 2600   34 111 26 18   Rhyncophorus phoenicis (larva) 2080 3520 330 22090 450   147 265 16 8   Tenebrio molitor (adult) 640 7630 1670 9370 1740 5260 60 127 21 11 0.4 Tenebrio molitor (larva) 440 7480 2100 8950 1410 4910 54 137 16 14 0.7 Zophobas morio (larva) 420 5630 1180 7510 1130 3610 39 73 9 10 0.3 Orthoptera                       Acheta domesticus (adult) 1320 9580 1090 11270 4350 7370 63 218 20 37 0.6 Acheta domesticus (nymph) 1200 11000 990 15370 5890 9690 93 297 22 39 0.4 Brachytrupes sp. 3300 6120   10360 2120   539         Crytacanthacris tatarica 1180 6450   9330 1370   128         Gryllotalpa africana 2630 8820   9300 3370   1448         Isoptera                       Macrotermes bellicosus (alate) 450   280 1170               Macrotermes subhyalinus (alate) 400 4420 4210 4810 19880   76   137 644   Nasutitermes corniger (soldier) 3700 2900 1500 5800 600   1001 164 33 115 0.5 Nasutitermes corniger (worker) 2000 4000 1300 6100 2400   394 144 52 32   Hymenoptera                       Aphis melifera (larva) 590 7720 910 11590 550 3750 56 69 17 3 0.3 Oecophylla smaragdina 1840 7920   8530 2160   219         Oecophylla virescens 800 9360 1220 9570 2700   1090 169 22 63   Diptera                       Drosophila melanogaster (adult) 1400 11000 1300       454 147 9 16   Musca autumnalis (pupa) 24800 27400 11500 5500 1800   250 270 15 660   Musca domestca (pupa) 9300 14300   8800 5600   465 275 34 370   All insects contain high levels of phosphorus, which results in a calcium:phosphorus ratio of less than one. For most monogastric animals, phosphorus from animal sources is virtually 100% available, while plant-based phytate phosphorus is approximately 30% available. The phosphorus in most insects is likely to be readily available as was shown for Musca autumnalis puparia with an availability of 92%. Most insects contain substantial levels of the other macro-minerals, magnesium, sodium, potassium and chloride. The very high sodium levels for the three species of lepidopteran larvae (Imbrasia ertli Rebel, Usta Terpsichore M. & W., and Conimbrasia belina Westwood) and for the termite, Macrotermes subhyalinus Rambur, is probably a result of salt added during processing. Most insects appear to be good sources of the trace minerals of iron, zinc, copper, manganese and selenium. For insects prepared for human consumption, some of the elevated levels of iron and copper are likely the result of metal that has leached from the cookware. Mineral composition in general probably largely reflects the food sources of the insect, both that which is present in the gastrointestinal tract and that which is incorporated into the insect's body as a result of the food it consumed. Studies of wild insects show both seasonal variation as well as variations between different populations of the same species living in the same general area. While it is assumed the availability of these trace minerals is good, there are no published studies measuring the availability of trace minerals in insects. There are a number of published reports on the amino acid composition of insects but recovery (measured as the percent of total nitrogen as amino acids) ranges from approximately 40 to 95%. This could be the result of the presence of large amounts of nitrogen-containing compounds other than amino acids, such as chitin, or methodology problems in the analysis. Because many papers report only a limited number of amino acids (usually those considered essential for humans), it is impossible to calculate recoveries and evaluate the accuracy of the data. In spite of these issues, there are sufficient data to show that insects are a good source of amino acids and provide good quantities of the essential amino acids. Because some of these amino acids are part of the exoskeleton and may be sclerotized, they may not be readily available when consumed. The only two studies measuring protein digestibility of insect protein in rats reported values of 86% and 89% values, which are only slightly lower than the values reported for other animal protein sources (egg 95%, beef 98%, and casein 99%). Thus, it is likely that overall, the digestibility of insect protein, while slightly lower than that of more traditional animal protein sources such as egg, meat and milk, is higher than that of many vegetable-based proteins. Crude protein and amino acid content of selected insect species.   Crude protein (%) Ala (%) Arg (%) Asp (%) Glu (%) Gly (%) His (%) Ile (%) Leu (%) Lys (%) Met (%) Cys (%) Phe (%) Tyr (%) Pro (%) Ser (%) Thr (%) Trp (%) Val (%) Amino acid analyses from a variety of papers provide no common estimate of the first limiting amino acid for insect protein. While tryptophan is the amino acid most commonly cited as first limiting, all of the amino acids known to be essential for humans have been reported as first limiting. They include histidine, isoleucine, leucine, lysine, total sulfur amino acids (methionine plus cystine), total aromatic amino acids (phenylalanine plus tyrosine), threonine and valine. While it is unlikely that all species of insects would have the same first limiting amino acid, the range of first limiting amino acids reported is difficult to understand, but may be due to the analytical techniques used. Accurate analysis of methionine, cystine and tryptophan requires two separate hydrolysis versus that used for the other amino acids and the low values reported in some papers suggest this was not always done. Another issue confounding the identification of the limiting amino acid is the use of a variety of different standards. Insect amino acid patterns have been compared to World Health Organization recommended patterns for both adults and preschoolers, United Nations Food and Agriculture Organization recommended patterns for pre-school children as well as comparisons to egg protein, or other reference proteins. In contrast to the variability obtained when calculating the first limiting amino acid, results from feeding studies have been very consistent. When diets containing insect protein from housefly pupae, yellow mealworm larvae, or Mormon crickets were fed to young, growing rats, in all three studies, methionine was shown to be the first limiting amino acid. While methionine was the first limiting amino acid for the growth of rats, when Mormon cricket meal was used as the sole source of dietary protein, no additional response was observed at maintenance, suggesting a different amino acid (not yet identified) was first limiting. As such, insect protein is likely to have a different first limiting amino acid when compared to human standards for either growth or maintenance. The high choline content of most insects also needs to be considered when determining the first limiting amino acid in insects, because high dietary choline levels can reduce the dietary requirement for methionine. Unlike birds, reptiles, and fish, mammals are ureotelic, excreting urea as an end product of protein metabolism. Arginine is synthesized during this process, which is why the arginine requirement for growing rats is low relative to that for birds or fish. This is why Mormon cricket meal was shown to be co-limiting in the amino acids arginine and methionine when fed to broiler chicks, while only methionine was first limiting when fed to growing rats. As such, the use of insects in poultry or fish diets may require different amino acid supplementation than when used in diets for mammals. In general, feeding trials using house fly larvae and pupae, face fly pupae, soldier fly larvae, Hermetia illucens (L.), Mormon crickets, house crickets, yellow mealworms, and various species of lepidopteran larvae have resulted in good growth of rats, chickens and several species of fish. This suggests that insect protein is readily available with protein quality values similar to, or slightly higher than, that of fish meal or soybean meal. However, in five separate studies, (three that used silkworm pupal meal) dried insect meals have produced poor results. In most of these studies, the poor growth appears to be a result of low food consumption. These results may be due to the presence of oxidized fats. Because dried insect meals are generally high in unsaturated fatty acids, they are susceptible to oxidation if not treated with an antioxidant during drying and storage. Another possibility is the presence of a compound in the insect meal, which negatively affects palatability. In the wild, many insect species are known to sequester compounds from their foodplants, which cause them to be unpalatable or toxic. A third possibility is the effect of some unknown anti- nutritional factor present in some species of insects. While there is little work in this area, a thiaminase recently has been discovered in both African silkworm pupae (Anaphe) and domestic silkworm larvae (Bombyx mori). There is only very limited data available for vitamin analyses of insects. While several species of lepidopteran larvae and the soldiers of one species of termites (Nasutitermes corniger) contain significant quantities of preformed vitamin A (retinol), in general, insects do not appear to contain much preformed vitamin A. Insects use a variety of retinoids for vision, which they synthesize from carotenoids in their food. As these retinoids are present only in the insect eye, whole body levels of retinoids are usually very low. There is a single report that honey bee (Aphis mellifera) larvae and pupae contain extremely high levels of preformed vitamin A (50,000 to 154,600 µg retinol/kg dry weight), but the analytical procedure used is not specific for retinol. More recent analysis using high pressure liquid chromatography detected no retinol in honey bee larvae or pupae, and only low levels (850 to 930 µg retinol/kg) in adult bees. Vitamin content of selected insect species.   Vitamin A (µg retinol/kg) β-Carotene (ug/kg) Vitamin E (mg α-tocopherol/kg) Thiamin (mg/kg) Riboflavin (mg/kg) Niacin (mg/kg) Pantothenate (mg.kg) Pyridoxine (mg/kg) Folate (mg/kg) Biotin (mg/kg) Vitamin B12 (ug/kg) Choline (mg/kg) ND – Not Detected Lepidoptera                         Bombyx mori (larva fed artificial diet) 2740 ND 34 19.1 54.3 152 125 9.5 4.1 1.4 ND 6523 Bombyx mori (pupa)           11             Conimbrasia belina (larva) 60 10   5.8 49.8 119             Galleria mellonella (larva) 40 ND 21 5.6 17.6 90 49 3.1 1.1 0.7 ND 3953 Imbrasia epimethea (larva) 470 82   1.8 43.0 118 ND 0.7 0.1 0.3 0.2   Imbrasia ertli (larva)                         Imbrasia truncata (larva) 330 71   2.9 55.0 118 ND 0.4 0.4 0.5 0.3   Nudaurelia oyemensis (larva) 320 68   1.6 34.0 101 ND 0.5 0.2 0.3 0.2   Porthetria dispar (adult with eggs) 100   149                   Usta terpsichore (larva)       40.4 20.9 3             Coleoptera                         Rhyncophorus ferrugineus (larva)       2.7 14.6 125             Rhyncophorus palmarum (larva)   18000 347                   Rhyncophorus phoenicis (larva)       33.8 25.1 34             Tenebrio molitor (adult) ND ND ND 2.7 23.4 155 66 22.4 3.8 0.8 15.4 6671 Tenebrio molitor (larva) 240 ND 20 6.3 21.3 107 69 21.1 4.1 0.8 12.3 4839 Zophobas morio (larva) 290 ND 21 1.5 17.8 77 46 7.6 1.6 0.8 10.1 4124 Orthoptera                         Acheta domesticus (adult) 240 ND 43 1.2 110.7 125 75 7.5 4.9 0.6 174.3 4932 Acheta domesticus (nymph) 140 ND 28 0.8 41.5 143 115 7.6 6.3 0.2 380.8 4776 Blatella germanica (not specified) 300   179 Brachytrupes sp.       9.7 66.7 86     Crytacanthacris tatarica       8.1 24.5 286             Gryllotalpa africana       6.9 65.6 167             Oxya verox       3.4 78.4 100             Isoptera                         Macrotermes subhyalinus (alate)       1.3 11.5 46             Nasutitermes corniger (soldier) 20400   84 Nasutitermes corniger (worker) ND   ND Hymenoptera Aphis melifera (adult female) 850 27   Aphis melifera (adult male) 930   10 7258                 Aphis melifera (larva) ND ND ND 17.7 39.2 158 51 5.1 ND 1.0 ND   Oecophylla smaragdina       9.2 33.8 130             Diptera                         Drosophila melanagaster (adult) ND   15                   While commercially raised insects appear to contain little or no β-carotene, most wild-caught insects contain a variety of carotenoids (astaxanthin, α-carotene, β-carotene, lutein, lycopene, zeaxanthin, and others), which they accumulate from their food. Most species of vertebrates can convert some of these carotenoids to retinol, so insects containing high levels of carotenoids may be a significant source of vitamin A for insectivorous vertebrates. There is little data on the vitamin E content of insects, but levels are generally low. Wild-caught insects appear to contain more vitamin E than cultured insects, which likely reflects differences in their dietary intake. When mealworms (Tenebrio molitor larvae) or house crickets (Acheta domesticus) were fed diets high in vitamin E for seven days, there was only a small increase in the vitamin E content of the crickets and the mealworms. It is not clear whether this reflects vitamin E absorbed by the insect, or is simply a result of the dietary vitamin E retained in the gastrointestinal tract. B-vitamin analysis of insects is very limited and most of the available data is for thiamin, riboflavin and niacin. All insects tested contained substantial quantities of most of the B-vitamins and choline. It should be noted that several B- vitamins (most notably thiamin and, to a lesser degree, pyridoxine and folic acid) are not heat stable so, processing insects by canning, roasting or boiling is likely to result in a reduction of these vitamins. While insects appear to be a good source of most B-vitamins, a number of insects appear to contain low levels of thiamin. Some of these low levels are likely an effect of heat processing, although the low levels seen for house crickets and superworms (Zophobas morio larvae) are for raw, whole insects. Recently, wild African silkworm pupae (Anaphe) have been shown to contain high levels of an enzyme which results in the destruction of thiamin (Vitamin B₁). This thiaminase was shown to be relatively heat stable and appears to be responsible for an acute seasonal ataxia reported in humans in Nigeria that was previously linked to Anaphe consumption. There are numerous reports on the fatty acid composition of various insect species, and all of the insects tested contained the essential fatty acid linoleic acid (18:2). There appears to be no consistent pattern in fatty acid profiles across a variety of insect species, although all species contained significant quantities of palmitic, oleic, linoleic and linolenic acid. Some insects have also been shown to contain minor amounts of other fatty acids including lauric acid (12:0), myristoleic acid (14:1), heptadecanoic acid (17:0), heptadecenoic acid (17:1), arachidonic acid (20:4) and benhic acid (22:0). Crude fat content and major fatty acids of selected insect species.   Crude fat (%) Myristic acid (14:0) Palmitic acid (16:0) Palmitoleic acid (16:1) Stearic acid (18:0) Oleic acid (18:1) Linoleic acid (18:2) Linolenic acid (18:3) Arachidic acid (20:0) Other fatty acids¹ ND – Not Detected ¹ Other major fatty acids reported as % followed by fatty acid formula Lepidoptera                     Bombyx mori (larva fed artificial diet) 8.1 ND 0.98 0.03 0.72 1.86 2.05 0.83 0.06   Bombyx mori (pupa) 37.1   9.72   2.60 13.69 1.56 9.53     Galleria mellonella (larva) 60.0 0.10 19.18 1.23 0.82 29.88 3.66 0.27 0.07 0.07%–17:1 Heliothis zea (larva fed broad-beans) 18.2 0.10 3.80 0.20 0.40 3.30 1.50 5.50     Heliothis zea (larva fed artificial diet) 30.2 0.10 7.60 2.90 0.10 12.90 0.70 0.00     Imbrasia epimethea (larva) 13.3 0.08 3.09 0.08 2.94 1.12 0.93 4.67     Imbrasia ertli (larva) 12.2 0.12 2.68   0.05 0.24 2.44 1.34 4.63 0.11%–17:0; 0.06%–12:0 Imbrasia truncata (larva) 16.4 0.03 4.03 0.03 3.56 1.21 1.25 6.04     Nudaurelia oyemensis (larva) 12.2 0.02 2.66 0.07 2.82 0.68 0.70 4.34     Usta terpsichore (larva) 9.5 0.22 2.60   0.01 0.16 2.58 0.27 0.71 2.82%–17:0 Coleoptera                     Rhyncophorus phoenicis (larva) 46.8 1.17 16.83   0.14 14.03 12.16 0.94 0.28 0.65%–17:0 Tenebrio molitor (adult) 14.9 0.22 2.34 0.17 0.72 4.93 3.77 0.11 0.06 0.06%–17:0; 0.06%–17:1 Tenebrio molitor (larva) 35.0 0.76 6.01 0.92 1.02 14.15 9.13 0.37 0.08 0.08%–17:1 Zophobas morio (larva) 42.0 0.40 12.54 0.17 2.99 15.68 7.81 0.26 0.10 0.17%–17:0; 0.17%–17:1 Orthoptera                     Acheta domesticus (adult) 22.1 0.13 5.06 0.29 1.88 5.00 7.44 0.19 0.13 0.10%–22:0 Acheta domesticus (nymph) 14.4 0.08 2.66 0.14 1.27 2.79 4.80 0.18 0.11   Isoptera                     Macrotermes bellicosus (alate) 46.1 0.08 21.45 0.96   5.92 15.87 1.77     Macrotermes subhyalinus (alate) 46.5 0.42 15.35   0.65 4.42 20.04 1.40 0.19 1.21%–17:0; 0.23%–14:1; Nasutitermes corniger (soldier) 11.2 0.48 0.85 0.11 1.33 3.66 1.24 1.09 0.43 1.03%–20:4; 0.49%–22:0 Nasutitermes corniger (worker) 2.2 0.09 0.21 0.05 0.28 1.08 0.33 ND 0.04 0.04%–12:0; 0.03%–22:0 Hymenoptera                     Aphis melifera (larva) 20.3 0.52 6.34 0.10 1.83 7.84 0.15 0.16 0.10 0.07%–12:0 In a review of insect fatty acid patterns, Thompson reported that several insect orders appeared to have unique fatty acid profiles. These peculiarities included relatively high levels of myristic acid (14:0) in Hemiptera, and palmitoleic acid (16:1) in Diptera. It also appears that linoleic acid (18:2) and linolenic acid (18:3) were virtually absent in Dictyoptera (Mantodea, Blattodea). The data are not shown in the table because crude fat and fatty acid content as a percent of body weight could not be calculated. In general, it appears that insect fatty acid levels reflect a combination of insect fatty acid synthesis (certain pathways that may be unique for certain species or orders) and the fatty acid composition of the insect's diet. For insects that feed on a single foodplant, the values in the table are probably typical for all members of the species. In contrast, the fatty acid content of generalist feeders like the house cricket, Acheta domesticus, is likely to vary widely depending on the diet being fed. In addition, the data for Rhyncophorus phoenicis (F.) and Macrotermes subhyalinus is for insects that were fried prior to analysis. As such, these analyses reflect both the fat naturally in the insect and that from the cooking oil. References Barker, D., M. P. Fitzpatrick, and E. S. Dierenfeld. 1998. Nutrient composition of selected whole invertebrates. Zoo Biology 17: 123–134.   Bukkens, S. G. F. 1997. The nutritional value of edible insects. Ecology of Food and Nutrition 36: 287–319.   DeFoliart, G. R. 1989. The human use of insects as food and as animal feed. Bulletin of the Entomological Society of America 35: 22–35.   Feltwell, J., and M. Rothschild. 1974. Carotenoids in thirty-eight species of Lepidoptera. Journal of Zoology 174: 441–465.   Finke, M. D., G. R. DeFoliart, and N. J. Benevenga. 1987. Use of a four-parameter logistic model to evaluate the protein quality of mixtures of Mormon cricket meal and corn gluten meal in rats. Journal of Nutrition 117: 1740–1750.   Finke, M. 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