Darna L Dufour & Joy B Sander. Cambridge World History of Food. Editor: Kenneth F Kiple & Kriemhild Conee Ornelas. Volume 1. Cambridge, UK: Cambridge University Press, 2000.
In the title of a delightful little book published in 1885, Vincent Holt asks, Why Not Eat Insects? The “why not” is hard to explain logically, nutritionally, or on the basis of the sheer abundance of these creatures. However, for Europeans and North Americans the eating of insects, or entomophagy, is considered a curiosity at best. And for many the idea is downright repulsive. Insects as food are found only in cartoons, or perhaps on the odd occasion when suitably disguised under a layer of chocolate. Yet for these same people, other invertebrate animals, such as oysters, snails, crayfish, and lobsters, are not only accepted as food but even viewed as delicacies.
In many other parts of the world, however, insects are considered good to eat and are appreciated for their taste as well as nutritional value. Some, like the giant queen ants (Atta sp.) of Colombia, are prized as delicacies and supposedly function as aphrodisiacs as well. Others, like the mompani worms of Africa, are frequently included in the diet and much enjoyed. Still others, like the cock chafer grubs of Ireland, although not much esteemed, have been used when more desirable foods were not available.
The purpose of this chapter is to present an overview of the role of insects in the diet in different parts of the world and in different time periods. We first review the use of insects as food within major geographical areas, in the present as well as in the historic and prehistoric past when information is available (a comprehensive list of insect species used as food is provided in Table II.G.15.1). We then summarize general patterns of insect use and provide information on the nutritional value of some commonly consumed insects.
Insects around the World
North America. The use of insects as food is generally frowned upon in North America, notwithstanding the repeated attempts by entomologists to make them more appealing. One of the best known of such attempts is R. L. Taylor’s 1975 book, Butterflies in My Stomach, and the accompanying recipe guide, Entertaining with Insects (1976). The reasons that most North Americans do not include insects in their diets have to do with food preferences rather than nutritional value. The dietary exclusion of insects is sometimes justified by the assumption that many insects carry diseases and therefore eating them is dangerous, but there is little evidence to support such a notion (Gorham 1979).
The prohibition against eating insects among many contemporary North Americans can probably be traced to Europe. European colonists who settled in North America also had strong taboos against consuming insects. In fact, they originally classified the New England lobster as an insect and refused to eat it. But that was in the 1600s. Subsequently, the lobster has, of course, passed from the status of prohibited food to delicacy.
Native Americans, however, did not have the same prejudices against insects as food, and there are a number of ethnographic and historical accounts indicating their importance in the diet. The bulk of these reports are from the western United States, where the most heavily consumed insects were the larvae of the Pandora moth, grasshoppers, and Mormon crickets—insects that occur in great abundance during certain seasons and in certain places in the region.
Pandora moth larvae (Colorado pandora lindseyi) are large caterpillars found on a certain pine tree species, Pinus jeffreyii. They were reportedly collected in large numbers by Native American peoples, either by hand or by trenching around the bottom of trees when caterpillars descended to pupate in the soil (Fowler and Walter 1985). As recently as 1981, Pandora moth larvae were still being collected (Fowler and Walter 1985).
Grasshoppers were also frequently consumed by early Americans. They occurred in large swarms or “plagues” in drier areas at densities of more than 12,000 insects per square mile in California (Brues 1946). On the beaches of the Great Salt Lake in Utah, grasshoppers washed up by the lake can pile up in long windrows as much as 20 centimeters thick, already salted and sun-dried (Madsen 1989). The return rates for collection in kilocalories (kcal) per hour are greater than for any other known collected resource (Madsen and Kirkman 1988). Grasshoppers are relatively high in some B vitamins and can be stored (dry) for long periods in the form of flour (Sutton 1988).
Crickets are another valuable food resource; they were often collected in large quantities in trenches and stored for use in the winter (Sutton 1988). One of these was the Mormon cricket (Anabrus simplex), so named because Mormons tried to kill these crickets off in the late 1800s and in the process caused animosity between themselves and Paiutes (Madsen and Kirkman 1988). There is some indication that insects formed an increasingly substantial part of the Native American diet as the local habitat was modified by European newcomers (Sutton 1988).
Other insects used by the first Americans were shore flies (Hydropyrus hians), available in great abundance in some locations, and ants that were made into flour soup (Sutton 1988). Judging by historical accounts, grasshoppers and crickets were usually roasted and ground with pine nuts, grass seeds, or berries to make cakes, which could then be sun-dried and stored. These were called “desert fruitcakes” and (interestingly) were considered a delicacy by European travelers as well as by Native Americans (Madsen 1989).
Central America and the Caribbean. In Mexico, J. R. E. de Conconi and collaborators (1984) have documented the consumption of a very wide variety of insects. They found 101 species of insects regularly consumed, fresh, roasted, or fried, at various stages of development. These belong to 31 families in nine orders and include dragonflies, grasshoppers, bugs, lice, treehoppers, cicadas, caddis flies, butterflies, moths, flies, ants, bees, and wasps (Conconi et al.1984).
Entomophagy has been practiced for a long time in Mexico (Conconi and Bourges 1977), where many insect dishes are considered delicacies. A well-known example is ahauatle, a mixture of hemiptera eggs. It was first reported in 1649 by Francisco Hernandez and was still consumed in 1933 (Ancona 1933). The eggs, from four species of aquatic hemiptera (two species of Krizousacoriza and two of Corisella), were collected on specially prepared bundles of leaves left in the lake water for several days during the principal egg-laying season. This mixture of eggs (said to have a shrimp-like flavor) was then fried with chicken eggs. The insect eggs were also dried and used as a condiment in the preparation of a traditional Christmas Eve dish,revoltijo.
The adult insects of both Krizousacoriza and Corisella were also consumed, usually along with a fifth species, Notonecta unifasciata. The adults were gathered in baskets, sun-dried, and sold on the street, as mosco para los pájaros. They were also ground and made into small cakes that were grilled. Both the eggs and adults of these species of aquatic insects were sold as fish food in Europe and in the United States (Ancona 1933).
South America. The giant queen ants of the genus Atta are prized as a gastronomical delicacy in Colombia. Atta are leaf-cutting ants considered to be a major pest in some agricultural areas. The queens of the genus are very large ants that swarm in the early rainy season and can be easily collected as they leave the nest. The gathering and toasting of these ants is a prosperous cottage industry in northeastern Colombia, and they are marketed throughout the country. Ant consumption can be traced to precolonial times: Gonzalo Jimenez de Quesada, founder of the Colombian capital, Santa Fe de Bogotá, described their use by local peoples in the highlands in 1555 (Nación 1989).
The consumption of a wide variety of insects (representing 10 orders and more than 50 different species) has been reported among Amerindian groups in South American rain forests. The insects that appear to be most commonly consumed are ants of the genus Atta, palm grubs, and caterpillars of various sorts. The consumption of the queen ants occurs throughout the Amazon Basin (Wallace 1853; Bodenheimer 1951; Denevan 1971; Weber 1972; Ruddle 1973; Dufour 1987). The first description of their use was provided by the naturalist Alfred Wallace (1853: 242-3):
The part eaten is the abdomen, which is very rich and fatty from the mass of undeveloped eggs. They are eaten alive; the insect being held by the head as we hold a strawberry by its stalk, and the abdomen being bitten off, the body, wings and legs are thrown down to the floor, where they continue to crawl along apparently unaware of the loss of their posterior extremities.
Palm grubs, or palm worms, are the large, fatty, legless larvae of wood-boring weevils (genus Rhynchophorus) found in the pith of felled palm trees. The weevils are ubiquitous in tropical rain forests, and the utilization of their larvae as a valued food has been widely reported (Bodenheimer 1951; Chagnon 1968; Clastres 1972; Beckerman 1977; Lizot 1977; Milton 1984; Dufour 1987). E. Bancroft, writing in the eighteenth century, claimed they were also highly esteemed by Europeans in Surinam, particularly by the French, who mixed the roasted grubs with bread crumbs, salt, and pepper (Bancroft 1769, cited in DeFoliart 1990). In northwest Amazonia they are eaten both raw and after smoke-drying over a slow fire, as components of normal meals and as snacks. Amerindians “cultivate” palm grubs in the sense that they fell palm trees with the expectation that they will be invaded by weevils and a crop of grubs will be available for harvest in two to three months (Clastres 1972; Beckerman 1977; Dufour 1987).
The consumption of other types of grubs or larvae is frequently mentioned in ethnographic reports. In the northwest Amazon, the larvae of wood-boring beetles are extracted from felled trees (Dufour 1987). One group of Amerindians in the Peruvian montaña region “cultivate,” or at least protect, an unidentified grub called poshori, found in piles of maize cobs (Denevan 1971).
Caterpillar eating has been reported for a number of Amerindian groups (Lizot 1977; Dufour 1987), but the actual species eaten have been identified for only one group—the Yukpa (Ruddle 1973). In the northwest Amazon region, five different species of caterpillars have been collected, two of them in large amounts (Dufour 1987). Less commonly ingested are soldier ants, termites, wasp and bee brood, and other larvae (grubs) of various sorts. The consumption of adult beetles seems to be even less common, but it has been reported for the Yukpa (Ruddle 1973) and Ache (Hurtado et al. 1985).
Although entomophagy is no longer common in Europe, insects were eaten throughout the continent at one time. Cock chafer grubs were consumed by peasants and mountain inhabitants until the 1800s and were an important source of protein in Ireland during the famine of 1688 (Bodenheimer 1951). In earlier times, those who could not afford a diet rich in protein and fat relied on insect sources to supplement their predominantly carbohydrate intake (Bodenheimer 1951).
The Greeks and Romans, who heavily influenced European culture, enjoyed insects as a food source (Bequaert 1921). Ancient Greeks apparently considered grasshoppers a delicacy, and even Aristotle reported eating cicadas. He considered them tastiest just before the final instar, but females, laden with eggs, were deemed delicious as well (Bates 1959). The Greeks and Romans also ate a large Melolonthid grub thought to be Lucanus cervus, which, according to Pliny, was fattened before consumption (Bequaert 1921).
The consumption of insects in Africa is still quite widespread (DeFoliart 1989), with caterpillars among the most popular. A recent survey found that 69 percent of Africans interviewed had eaten one or more species of caterpillar or lived in households where at least one species of caterpillar was consumed (Ashiru 1988). The mopanie worm (Gonimbrasia belina), the so-called snack that crawls, is one of the best-known edible caterpillars. It is eaten fried, dried, stewed in tomato sauce, and even raw (Brandon 1987). Mompani worms appear to constitute an important source of protein for rural dwellers (Ivbijaro 1990) and were reportedly preferred to meat in some areas when they were in season (Quin 1959).
Caterpillars have become something of a trend on menus around Africa and are currently marketed by a firm in Johannesburg (Brandon 1987; Zimbawe Herald 1988). Because they occur in large aggregations, the collection of caterpillars is easier than that of some other insects (Chavanduka 1975). In fact, collection rates of 40 pounds per day have been reported (Brandon 1987).
Locusts also play a significant role in the diet of Africans, particularly Schistocerca gregaria, the desert locust (Quin 1959; DeFoliart 1989). Indeed, in the notso-distance past, the locusts have been so popular that locust swarms were welcomed and their arrival attributed to a mighty spirit (Bequaert 1921). The female locusts loaded with eggs were most commonly eaten, and often a soup was made of the eggs (Berensberg 1907; Bequaert 1921). High in protein and fat, locusts may be an excellent supplement to local diets that consist mainly of carbohydrates (Chavanduka 1975). P. J. Quin (1959) also notes that locusts played a significant role in sustenance and were the most popular meat of all among the Pedi of the Transvaal.
Termites are also utilized as food in Africa, especially during the early rainy season when the reproductive forms fly from the nest in large swarms and can be collected (Brickey and Gorham 1989; Kumar 1990). At one time, termites were such an important addition to the diet that their mounds were fought over as property (Bequaert 1921). Local people knew when these swarms would occur and they would cover mounds for purposes of collection (Curran 1939). Termites can be eaten raw (with care taken to avoid being bitten by the termite first) (Curran 1939) and fried, and they are also roasted. Termites not only are high in fat and protein but also contain a significant amount of lysine, which is not found in maize, a main constituent of the African diet (Chavanduka 1975; Oliveira et al. 1976).
Palm grubs, such as those of the genus Rynchophorus, are still consumed in Cameroon, Angola, and other parts of Africa and are occasionally raised specifically for this purpose (Oliveira et al. 1976; DeFoliart 1990). They may be prepared by stewing, frying, or grilling, but one creative recipe suggests boiling them inside coconuts instead (Grimaldi and Bikic 1985, cited in DeFoliart 1990).
Although a recent study indicates that 10 percent of the animal protein in the diet of local people in Zaire comes from insect foods, the general trend in Africa is toward a reduction in entomophagy (DeFoliart 1990; Kumar 1990). This development is, perhaps, due to an increased use of pesticides as well as to exploitation of new habitats in order to accommodate growing populations, both of which have reduced the number of insects to which populations have access (Chavanduka 1975).
Middle East and South Asia. With the exception of locusts, whose consumption continued into recent times, the Middle East and South Asia have not had a strong history of entomophagy (Bodenheimer 1951). The desert locust, S. gregaria, was a major source of food in the Middle East, with up to 9,000 kilograms gathered per day in some areas (DeFoliart 1989). These locusts were prepared by cooking in salt water and then sun-drying, after which they were traded at the market (DeFoliart 1989). During times of famine locusts were frequently ground into flour from which fried cakes were made (Bodenheimer 1951). In 1988, Saudi Arabians were also observed eating locusts, grilled like shrimp, after the worst locust plague in 25 years descended on the west coast (San Francisco Chronicle 1988).
Locusts were especially prevalent in the diet of nomadic people such as the Bedouins, who welcomed the periodic swarms (Bodenheimer 1951). The best-known incident in that part of the world involving locust eating, however, concerns John the Baptist’s limited fare of locusts (St. John’s bread) and honey during his ordeal in the desert. He was observing the decree of Moses found in Leviticus 9:22: “These ye may eat; the locust after his kind and the bald locust after his kind, and the cricket after his kind and the grasshopper after his kind.”
A recent study of three tribes in Assam, India, has revealed a surprising number of locusts eaten on a mass scale (Bhattacharjee 1990). No other contemporary insect consumption is documented for South Asia except in Nepal. The Nepalese in the Himalayan foothills are said to prepare a native dish, called bakuti, in which the larvae and pupae of giant honeybees are extracted from the wax comb and cooked until they resemble scrambled eggs (Burgett 1990).
Southeast Asia. Entomophagy is still relatively popular in Southeast Asia. In fact, Thailand currently exports frozen steamed ant larvae and pupae to the United States as specialty foodstuffs (Brickey and Gorham 1989). In North Thailand, bee brood is prepared for consumption by steaming entire honeycombs wrapped in banana leaves (Burgett 1990). Such grubs and pupae must be an important food among local people because, as F. S. Bodenheimer (1951) notes, the collection of combs is done at great risk of being stung.
The consumption of beetles has been especially popular throughout Southeast Asia, with 24 species in six families listed by Bodenheimer (1951) alone. He reported that Dytiscid beetles, such as Cybister and Hydrophilid beetles, seem to have been the most frequently eaten and those most commonly sold at market (Hoffman 1947). The larvae of longicorn beetles and weevils were also sought by the people of Laos (Bodenheimer 1951). The larvae of Rhynchophorus schah, which are found in coconut palms, were roasted, and other Rhynchophorus larvae were fattened and sold for a good price at the market.
While in Laos and Siam (now Thailand) in the 1930s, W. S. Bristowe (1932) also noted the popularity of larval as well as adult beetles in this region. Among those he cited as favorites were dung beetles (Scarabaeidae), which were served curried, and the giant water beetle (Lethocerus indicus), a great delicacy that was said to taste like Gorgonzola cheese. Bristowe also observed dishes of water, set out with lighted candles in the center, to attract dragonflies and termites. These insects would singe their wings on the candles and fall into the water to be subsequently collected.
Bristowe (1932) claimed that the local people’s knowledge of the life history of these food insects was very thorough and that they truly enjoyed eating the insects and were not consuming them strictly out of necessity. Furthermore, he hypothesized that by eating pest insects the people were reducing the amount of damage done to their crops.
The green weaver ant (Oecophylla smaragdina) was used throughout South and Southeast Asia in a condiment as well as a drink; both were said to have a rather acidic flavor (Bequaert 1921).
East Asia. Insect consumption is still quite common in some parts of East Asia. Perhaps the most well-known insect eaten in this region is the pupae of the silk-worm Bombyx mori. These pupae are exported from Korea to the United States (Brickey and Gorham 1989) and are also eaten in China, according to a recent study done by the Institute of Insect Research in Yunnan Province, China (The Research Institute 1990). W. E. Hoffman (1947) observed that the pupae were sold throughout the silk district and often cooked immediately after the silk was unraveled, so as not to waste the valuable resource that accompanied the silk.
The larvae and pupae of Hymenopterans are another food resource currently used in East Asia. Five species of immature bees and wasps utilized as food were identified by the Institute of Insect Research in Yunnan Province. B. Hocking and F. Matsumura noted in 1960 that Japan had been exporting bee pupae in soy to the United States. Interestingly, one of the favorite dishes of Japan’s late Emperor Hirohito was wasp pupae and larvae over rice (Mitsuhashi 1988). Bodenheimer (1951) also documented the consumption of the larvae and pupae of Vespa, a wasp, in Japan.
Locusts are presently consumed in East Asia, particularly those of the genera Oxya and Locusta (The Research Institute 1990b). Bodenheimer (1951) described the sale of grasshoppers fried in sesame oil in the local markets in China earlier in this century. Other insects consumed in East Asia included L. indicus, the giant water beetle, and caterpillars infected with Cordyceps, a fungus. These caterpillars were tied in bundles by the fungus filaments and sold as a delicacy (Hoffman 1947).
Pacific Islands. According to V. B. Meyer-Rochow (1973), insect eating is still a part of the native cultures in Papua New Guinea. Most widely documented are the sago palm grub feasts in which hundreds of pounds of Rynchophorus bilineatus larvae are wrapped in banana leaves and roasted. In fact, three species of palm grubs are exploited regularly, along with other larvae and adults of large beetles including many of the family Scarabaeidae (Meyer-Rochow 1973).
New Guineans also consume a great number of Orthopterans, including two species of stick insects, two of mantids, and the female of a species of locust (Meyer-Rochow 1973). Meyer-Rochow hypothesized that insect consumption provided needed dietary protein and fat because the greatest variety and quantity of insects were consumed in areas with the highest population density as well as the lowest amounts of available animal protein.
Termites were also very popular in the Pacific Islands, especially the sexual winged forms, which are higher in fat content. The predominant species eaten, Macrotermes, were caught after they flew into fires, burning their wings. In the Philippines, natives were said to eat the locusts that consumed their potato vines—a unique form of pest control (Bodenheimer 1951).
Australia and New Zealand
Despite a general reduction in the use of insects as food worldwide, entrepreneurs in Australia have begun to introduce insects to their commercial food market (Putting Insects on the Australian menu 1990). The insects considered to have the best potential for success include black honey ants, witchetty grubs (the larvae of a Cossid moth), bardi grubs (the larvae of a Cerambycid beetle), and Trigona bees. All of these insects have been supplied from around Australia where they are local delicacies. Many restaurants in Australia also now include insects on their menus (Putting Insects on the Australian menu 1990).
The black honey ant (Camponotus inflatus) is similar to the honey ant found throughout North and Central America. A modified worker ant with an enlarged body the size of a grape and filled with nectar, the black honey ant was highly sought after by Aboriginal Australians (Bourne 1953) and even considered a totem animal by some clans (Flood 1987; Conway 1990). The digging up of these ants is considered an important traditional practice and is still taught to children (Conway 1990). Other species of ants were also important food resources for Aboriginal Australians (Bodenheimer 1951). Tasmanians had a number of words for the various ants that they identified, and traditional feasts were held during the periods that ant pupae could be obtained (Sutton 1990).
Witchetty grubs were also an important food of Australian Aborigines (Flood 1987). The name “witch-etty grub” refers to several types of grubs (Campbell 1926) and probably includes the larvae of the Cossid moth (Xyleutes leuchomochla), the giant ghost moth (Hepialidae), and the longicorn beetle (Cerambycidae) (Bodenheimer 1951; Sutton 1990).
Among the most unique and well-documented examples of entomophagy in Australia were the annual Bugong moth feasts that occurred in the Victorian Alps until the 1890s. Moths of Agrotis infusa migrate from the plains of New South Wales to aestivate (the summer equivalent of hibernation) every year in the rock crevices and caves of the Bugong Mountains, from which their name was derived (Flood 1987). Enormous numbers of moths have been counted (up to 17,000 per square meter) in some of these crevices and found on the floors of caves to depths of over 1 meter (Flood 1980). Many different tribes of Aboriginal Australians traditionally gathered to feast on the moths, and evidence of these feasts has been carbon dated to about 1,000 years ago (Flood 1980).The moths were smoked out by thrusting a burning bush into the cracks of the rock, then they were thrown into hot ashes or sand to remove the wings and legs (Campbell 1926; Flood 1980). These moths are said to have a nutty flavor and are high in both protein and fat (Campbell 1926; Sutton 1990).
Insects Are Good to Eat
General Patterns of Use
The great number and diversity of insect species (over 600) that have been or are used as food are listed in Table II.G.15.1. The largest variety of species appears to be in the tropics, which probably reflects the greater faunal diversity in these areas and the larger size of individual organisms. But it may also reflect to some extent the amount of research done on the topic in such climates. Comparatively fewer species appear to have been consumed in the more temperate regions of North America, Asia, and Europe. Fewer insect species inhabit these areas, and in general, the size of individual organisms is smaller.
A closer look at the insects listed in Table II.G.15.1 reveals that many of the same types of insects (i.e., in the same orders and families) are consumed in different parts of the world.The most widely consumed are probably the locusts (Acrididae), termites (Termitidae), and palm grubs (Curculionidae) (see Table II.G.15.2). These insects share two characteristics that are significant to their use as human food: (1) Individual insects are relatively large; and (2) individuals are highly aggregated during at least part of their life cycle. Locusts, for example, are among the largest of insects. They are also gregarious and can form swarms of thousands of individuals. Termites are generally smaller in size but are ubiquitous in tropical ecosystems. The species employed as food can be found in large, easily recognized colonies (for example, Macrotermes spp. in Africa), and the reproductive forms of some species can be easily captured during mating flights. Palm grubs, the larvae of weevils, can be as big as sausages. Over 50 percent of the Curculionidae reported are from the genus Rynchophorus, a genus found in the Americas, Africa, and Asia, which includes some of the largest of all herbivorous beetles (Crowson 1981). In addition, palm grubs can be harvested in sizable quantities from the pith of felled palm trees.
About 50 percent of the insects listed in Table II.G.15.1 are consumed in immature stages of the life cycle. The advantage to human consumers is that the immature stages are soft-bodied, typically high in fat, usually the largest form of the life cycle, and often in the stage of the life cycle when individual insects can be found in the greatest aggregations. In the order Lepidoptera (butterflies and moths), for example, the larval stage is the stage of the life cycle in which the insect is largest and has the highest energy (caloric) content. Compared to the larvae in the last instar, the adult forms have a lower body mass and a hardened exoskeleton, which reduces their digestibility. The larval stage is also often the stage of the life cycle at which the organisms are the most numerous and highly aggregated, whereas the adults are more mobile and widely dispersed. Furthermore, the larval stage is often long, as opposed to the shorter adult stage (Daly 1985), and therefore offers a greater harvesting opportunity.
Food Value of Insects
In terms of nutrition, insects are comparable to other animal foods. The composition of some insects consumed in tropical South America is shown in Table II.G.15.3, and values for two other common sources of animal protein—dried fish and dried meat—are provided for comparison. The energy value of the insects is high, between 425 and 661 kcal per 100 grams, with the energy values for female alate ants (Atta sp.) and Rhynchophorus larvae the highest, because both of these are rich in fat. The amount of protein in insects is also relatively high, but its quality appears to be somewhat lower than that of vertebrates (Conconi and Bourges 1977). In relation to more familiar foods, the composition of ants, palm grubs, and caterpillars is comparable to goose liver, pork sausage, and beef liver, respectively. The composition of termite soldiers is roughly comparable to that of non-oily fish, although the latter contain more protein.
Unfortunately, the actual nutritional importance of insects in human diets is not well understood because there is little information on quantities actually consumed.
Summary and Conclusions
Insects are ubiquitous and have been included in human diets in most areas of the world at some time. They are still a component of many current diets. The inclusion of insects in these diets should not be regarded as a mere curiosity, nor should their nutritional importance be overlooked because of their small size. Insects are not only a food prized by many peoples but also a good source of energy, animal protein, and fat. Their dietary importance varies from region to region and group to group, but the widespread practice of entomophagy deserves attention in any description or evaluation of human diets.