"What kind of insects do you rejoice in, where you come from?" the Gnat enquired. "I don't rejoice in insects at all," Alice explained . . .
Through the Looking Glass, Lewis Carroll
Dawdling down the aisles of tomatillos and tortillas, among the chocolate and chillies that jostle for floor space in the mighty markets of south-west Mexico, the slack-jawed visitor will eventually, inevitably, come face to beady face with an enormous bowl full of grasshoppers.
The gringo might be forgiven for mistaking these chapulines, fried with lime juice and garlic, consumed by the bagful, for vividly spiced shrimp - a comparison that would horrify traditionally minded local people, who, although barely 100 miles from the Pacific Ocean, consider the coastal taste for camarones a la plancha utterly repulsive. Prawns, it seems, are still a taboo food in parts of rural Oaxaca.
We, too, make similarly arbitrary distinctions - although, as Ronald L Taylor observes in Butterflies in My Stomach, his 1975 study of insects in human nutrition, it is less clear why we prize sea-dwelling arthropods such as lobsters and prawns, which "eat every kind of putrid flesh and fish they can find", yet shy away from the caterpillar or grasshopper, which "eats nothing during its entire life but clean, green plant material".
This curious fastidiousness is peculiar to those of European descent. According to Marcel Dicke, a professor of entomology at Wageningen University in the Netherlands, 80 per cent of the world's population include insects in their diets, and as those Mexican grasshoppers and the soft, chilli-spiked silkworms of Bangkok's night markets prove, it's not just those with little other choice. Indeed, Pliny the Elder notes that beetle larvae, fattened on a diet of wine and flour, were a great favourite at the aristocratic Roman table.
The Victorian naturalist Vincent M Holt, author of the hopefully titled Why Not Eat Insects?, reflected that our attitude "would not be so absurd if it were only the rich that were concerned, for they can afford to be dainty". It's a squeamishness, however, that we may no longer be able to sustain - thanks to population growth and increased appetites in the developing world, meat consumption is expected to double by 2050, yet livestock farming already occupies 70 per cent of the world's agricultural land. As Professor Dicke points out, rather than chopping down the rainforests to help fulfil the demand for meat, we desperately need to find an alternative source of protein.
Insects seem like the obvious option: they require no fertiliser and very little land or water to farm and, to add to their green credentials, generate a fraction of the emissions of cattle and other ruminants. They are quick to mature and multiply, are a good source of the nutrients lacking in most plant-based meat substitutes, and the UN is now investigating the practicalities of mass production as insurance against worldwide famine.
Just one of those dried Mexican grasshoppers, for instance, contains twice as much protein as the equivalent weight of beef, yet grows to maturity in half the time, and with a sixth of the feed per kilo of meat - insects are extremely efficient converters of food to body mass. This rapid growth means that, in one summer, a pair of houseflies may produce 191 quintillion descendants - and all on a diet of what is, in effect, rubbish. Taylor suggests that insects could be used in "advanced waste treatment" processes, with meat as the by-product, "thus making quality food out of materials we now turn loose to pollute our environment".
Such joined-up farming may sound happily futuristic, but Dicke claims that insects will be "an important part" of all of our diets before the decade is out. There are already a number of recipe books devoted to such novelties as "cockroach à la king" and sweet-and-sour silkworms, and Selfridges does a roaring trade in scorpion lollipops and Thai curry crickets - but I suspect all those legs will creep into our kitchens in more subtle forms.
Various species, from mealworms to water boatmen eggs, already make their way into fortified flours in Asia, Africa and the Americas, and Taylor argues a persuasive case for using insect nutrients to enrich protein-deficient foodstuffs. "If the consumer is squeamish," he explains, "the product could be labelled 'fortified with animal protein' . . . which would be absolutely true and might in fact serve to promote the sale of the product. Perhaps some would object to such labelling as misleading but the profound realities of world food need and possible mass starvation or malnourishment are going to force us to exploit every avenue for promoting the use of all our resources."
What Taylor views as a "senseless prejudice" may be difficult to overcome - but then, 30 years ago, who would have expected to see a sushi bar at Butlins? Back in 1885, Holt foresaw a time when "the slug will be as popular in England as its luscious namesake the Trepang, or sea-slug, is in China". He may not have lived to see that day, but it seems, whatever our feelings on the subject, that we just might.