Insect diversity may be the key to food security in traditional societies. It is likely that in some traditional societies, humans do not use all of the potentially edible insects. There are numerous lists of edible species in different societies, but information still needs to be gathered and confirmed if this valuable resource is to be used effectively.
It is essential that the names of edible species are confirmed scientifically for accurate exchange of information. Lists need to be regularly upgraded. Some older lists need to be reassessed because either: (i) those groups of people no longer use those insects; or (ii) there have been recent dietary changes; for example, in the Kaleum district of Sekong Province in Laos, the Katu considered belastomatid water bugs inedible, but have started to eat them in response to a decrease in other sources of protein (Krahn 2003).
There are still considerable knowledge gaps for known edible insects. While there may be a lot of information available for a few edible species, details are lacking for most species, including preparation methods and recipes. It is important to record and maintain traditional knowledge about edible insects while respecting traditional ways of life; for example, gender is often important in food harvesting, and in northeastern Thailand, women are the main collectors of insect food (Somnasang et al. 1998). The nutritional value of different edible species needs to be assessed (Ademolu et al. 2004; Fagbuaro et al. 2006). Research should also be undertaken on the value and the sustainability of products with a long traditional use history. For example, Cordyceps, a caterpillar whose body is taken over by a fungus (Clavicipitaceae), has a long history of human use in China and India (Holliday & Cleaver 2008). It is an important part of the Tibetan rural economy (Winkler 2008), but management plans are required for its sustainability because of the decline from overcollecting and other environmental factors such as grazing and firewood harvesting (Sharma 2004; Devkota 2006).
The consumption of plant pests is sometimes advocated to reduce damage and to reduce pesticide usage. Many plant pests have high nutritional value; for example, Cirina forda Westwood (Lepidoptera: Saturniidae) is added to vegetable soups in Nigeria, where the larvae provide high levels of protein, minerals and polyunsaturated fatty acids to people whose diets are deficient in animal protein (Akinnawo & Ketiku 2000). An important question is whether collecting plant pests is an effective means of pest control. In the case of the variegated grasshopper Zonocerus variegates (Linné) (Orthoptera: Pyrgomorphidae) in the Cameroon, traditional hand collecting for human consumption does not have the same impact in reducing numbers as the late season rains (Kekeunou et al. 2006).
Supply can be unpredictable because of factors beyond the control of people at the local level. These include rainfall and extreme climatic conditions such as droughts and floods. The uncertainty of supply can be exacerbated by human factors: overexploitation of edible insects, bad land management practices (overgrazing, overharvesting of trees), conflict with other animals, conflict in land use and the availability of other food sources.
Traditional owners have, in most cases, developed harvesting protocols and habitat management practices that ensure sustainability. These include the timing of fire, if appropriate, in habitat management (DeFoliart 1997). Problems can arise when there are market demands that encourage non-specialist harvesters to collect, such as the case of mopane worms Gonimbrasia belina Westwood (Lepidoptera: Saturniidae) in Zimbabwe (Maviya & Gumbo 2005).
With changes in land tenure, such as the establishment of nature conservation reserves to protect remnant habitats and wildlife, conflict can arise from preventing the harvesting of food by traditional owners (DeFoliart 1997), or competition can develop between protected wildlife and local villagers such as the conflicting uses of woodlands by elephants and humans for food and other products (Hrabar et al. 2009). There can be direct competition between humans and wildlife for edible insects, such as aardwolves and humans competing for alates of the termites Hodotermes mossambicus (Hagen) and Macrotermes falciger (Gerstacker) (Isoptera) during the rainy season (Kruuk & Sands 2008). One termite mound can result in 50 kg of termites and they can be preserved for up to one year by salting and sun-drying (Gardiner & Gardiner 2003).
While promoting the use of insects as food in traditional societies, it is important that only local species be used and if people decide to bring in species from elsewhere, that any potential adverse effects be determined beforehand. For example, the giant African snail Achatina fulica Férussac (Gastropoda: Achatinidae) is an edible species that can become a pest itself if taken out of its natural range (Mead 1961).
Traditional societies can achieve better food security through: (i) more knowledge about the range of edible insects that they could use; (ii) sustainable harvesting protocols; (iii) environmental management protocols; (iv) development of limited controlled production if appropriate; and (v) sustainable closed food production systems, if possible. However, it is important that edible insects are considered as part of the wider food spectrum of plants and other animals.
The risk of variability in insect numbers could be reduced by the development and adoption of closed production systems at the local level. These are either: (i) field manipulations of wild populations for sustainable harvesting; and/or (ii) small captive breeding programs such as those developed for snail farming in Africa (FAO 1986a,b). If possible, the development of controlled production systems that are more energy efficient (e.g. recycling organic waste) to produce edible insects for both livestock and human consumption would be ideal. These systems would not alleviate the problems caused by large livestock animals, but could be integrated with small aquaculture or with poultry production. Fishmeal is often used as a food item in aquaculture, and there are studies that indicate termites, and garden snail and other insect meals are effective food sources in aquaculture (Ogunleye & Omotoso 2005; Sogbesan & Ugwumba 2008).
Appropriate systems would need to be developed for different environments. In Laos, edible insects can be integrated into the FAO model for home gardens. The model's aim is to increase food production, diversify food production, increase food supply and availability and meet nutritional needs of households (Dyg & Phithayaphone 2004). This system could be linked to aquatic resources (including aquaculture) (Friend et al. 2004), management of adjacent ecotones for sustainable production (Nonaka 2008) and the use of forests for non-wood forest products (Foppes & Ketphanh 2004).
Not all insects are edible. Some contain toxins, either produced by the insect themselves or plants (DeFoliart 1992), and some people have allergies to insects (Auerswald & Lopata 2005). Some societies have managed to determine how to make apparently inedible species edible. In Africa, the edible stink bug Encosternum delegorguei Spinola (Hemiptera: Tessaratomidae) is available as adults in winter when the mopane worm is in the underground pupal stage. Stink bugs are made palatable by washing with warm water to make them release their pheromones (repeated three times), then boiled in water, killed and sun-dried. The armored ground cricket Acanthoplus spiseri Brancsik (Orthoptera: Tettigoniidae) is made edible by removing its gut after carefully pulling off its head, boiling for a minimum of 5 hours, frying in oil and serving with a relish of tomato and onion. Boiling is important as it removes the toxic substances that can cause severe bladder irritation. (Gardiner & Gardiner 2003; Toms & Thagwana 2003; Teffo et al. 2007). The methods developed to make inedible species edible are an important intellectual property of the traditional societies that discovered them.
The African silkworm Anaphe venta Butler (Lepidoptera: Notodontidae) is eaten in southwestern Nigeria. During the rainy season, many less-wealthy people have a high carbohydrate and low protein diet of cassava (which contains cyanogenic glycosides), and those who consume the silkworm larvae exhibit an acute ataxic syndrome. While these larvae provide high levels of protein, they lack the sulfur-containing amino acids (cysteine, methionine) required to detoxify the cyanogenic glycosides consumed in cassava. The seasonal ataxic syndrome is an acute thiamine deficiency due to the monotonous diet of carbohydrate meals containing cyanogenic glycosides. Their thiamine deficiency is exacerbated by consumption of anti-thiamine factors in Anaphe venata (Adamolekun 1993; Adamolekun et al. 1997).
Any living organism can be infected by microorganisms or parasites (Hardouin 1995). For example, the larvae of Bunaea alcinoe Stoll (Lepidoptera: Saturniidae) in the Niger Delta has high levels of enterotoxin-producing bacteria on the exterior surface of the body. The cooking process eliminates these bacteria (Amadi et al. 2005). The quality of stored mopane worms also deteriorates due to bacteria, fungi and insects (Mpuchane et al. 2000). These issues can be simply overcome through the development of protocols for production, preparation, storage and transport, and appropriate education (Ghazoul 2006; Ohiokpehai 2006). This is important as increased urbanization has seen an increase in the purchase of food as street food (Ohiokpehai 2003).
A danger of eating harvested insects is pesticide residues. While health risks should be the main issue, often it is economic issues that decide whether insecticides are applied. In some cases, farmers may be reluctant to use insecticides because they affect edible insects and the value of edible insects may be greater than income from grain (Abate et al. 2000). Another example is rice-field grasshoppers in Korea; numbers declined with insecticide use, but a decline in pesticide use and a desire for pesticide-free rice resulted in a resurgence in sales of these insects, with financial benefit to farmers (Pemberton 1994). Other examples of reduced pesticide use to increase edible insects are found in the Philippines and Thailand (DeFoliart 1997).
While use of individual insect species as food is important, the development of multiple-product food–insect systems can be of greater benefit (DeFoliart 1997). Mopane worms can be used as either human or livestock food; they need to be gutted for human consumption but not if fed to livestock because the livestock benefit from fiber in the guts (Madibela et al. 2007). Another approach is to consider a particular plant as a source of multiple food products: the mopane tree Colophospermum mopane is host to mopane worms, the sweet wax–producing psyllid Arytaina mopane Pettey (Hemiptera: Psylloidea) and edible honey (Mojeremane & Lumbile 2005). Edible insects can provide an additional source of income for local communities; in Venezuela, the palm worm Rhynchophora palmarum (L) (Coleoptera: Curculionidae) is collected by Indian people as food but there is potential for them to develop small-scale production systems to sell the worm to tourists (Cerda et al. 2000).
There may be non-food values of insects, such as the use of insects for medicines or as cultural icons (Pemberton 1999). Examples include the edible Chinese black ant Polyrachis vicina (Shen et al. 2006) and hornets in Yunnan sold as medicine (soaked in spirits) or as luxury food (Matsuura et al. 1999). The caterpillar fungus Cordyceps sinensis is important for Tibet's rural economy because it is the single most important source of cash for rural households (40% of rural cash income). In 2004, 50 000 kg of this fungus was harvested and it was worth US$225 million to the Tibetan GDP. However, increased harvest pressures may not be sustainable (Winkler 2008).
Insects such as silkworms, bees and ants can be considered as multiple-product food–insect systems, meaning there are multiple uses for the species.
Silkworms have been cultivated for several thousand years to obtain silk fibers. However, the pupae are a high-quality source of protein and are comparable to the dietary profile recommended by FAO/WHO (DeFoliart 1995
; Mishra et al. 2003
; Zhou & Han 2006
). Silk production is widespread in Asia and Brazil (Speight 2001
), so there is potential to encourage the use of silkworms for both a valued product (silk) and a food source. Research is also underway on the use of the silkworm Bombyx mori
Linnaeus (Lepidoptera: Bombycidae) as part of bioregenerative life support system for space travel (Yu et al. 2008
Honey is a desired food item in many different societies (DeFoliart 1995
). Honey and edible insects are highly sought by the Mbuti of Eastern Zaire. The seasonality of these foods limits their importance to a few months each year. Honey production is also dependent upon mass flowering of nectar-providing bee-pollinated trees (Hart & Hart 1986
). The Hazda foragers of Tanzania collected honey, which has low crude protein levels, but has higher protein levels than American honeys because the Hazda do not remove the bee larvae from the combs as they are eaten (Murray et al. 2001
). Bees may be threatened by environmental changes and inappropriate management (overharvesting) by Mayans of the Yucatán peninsula (Villanueva et al. 2005
), highlighting the need to reinforce traditional methods of honey production by using native bees as a flagship for bee and forest conservation.
The Asian weaver ant Oecophylla smaragdina
Fabricius (Hymenoptera: Formicidae) is used in various ways globally, from human food to bird food and medical uses. They are very important as a food source and for additional income to the local community in Northeast Thailand (Sribandit et al. 2008
). Increasing numbers of ant collectors travel long distances to ants and increased harvesting pressure may threaten natural ant populations. Ant farming is suggested as a potential solution but it needs to be assessed in terms of viability, practicality and biological impacts on other insects (Sribandit et al. 2008
). Weaver ant husbandry is practiced in the Mekong Delta of Vietnam as a natural biological control of insect pests (Barzman et al. 1996
; Lim et al. 2008
) and there has been research on the use of weaver ant colonies for biocontrol of crop pests in Australia (Peng et al. 1999