The above question was posed by Vincent M. Holt in 1885 in his book of the same name, and now, having munched on a choice selection myself, I can offer an answer to that question: because they taste pretty awful and have a horrible texture to boot.
The topic was also the subject of a recent TED talk, in which Marcel Dicke proclaimed that insects can hold their own against meat in terms of flavour. Well, perhaps we were eating the wrong insects, but I would have to disagree with Marcel on that one, based on my own recent experience.
I was "lucky" enough to have the opportunity to try these rather undesirable delicacies at London's Natural History Museum on Friday night (that's right, I spend my Friday nights chomping on insects with strangers - what of it?) at an event called "Edible insects - food for the future?".
On the menu were meal worm larvettes (think larvae) and giant mole crickets as a starter, followed by a main of toasted weaver ants, bamboo worms and fried giant crickets, all topped off with a dessert consisting of toasted silkworm pupae and chocolate covered ant wafers.
With the exception of the meal worm larvettes (crunchy and slightly salty - a bit like puffed rice), everything on offer was less than delicious. "Musty" was probably the flavour that came to mind most often, and the bamboo worms and silkworm pupae had a worryingly cheesy or fishy taste.
"Something tells me these are never going to catch on," I though to myself as I picked a giant cricket's leg from between my teeth. The main contribution of the ants in the chocolate ant wafers was to spoil some otherwise perfectly good chocolate with an unpleasant bitter aftertaste. All in all, it was not a culinary experience I will be rushing to replicate.
Interest in eating insects has arisen again recently because of the ongoing human population boom. If there are nine billion people by 2050 as predicted, so the thinking goes, perhaps eating insects will help stave off the inevitable food shortages that will follow. And they are rich in protein, ubiquitous and cheap - it's just a shame they are so unappealing as foodstuffs.
Of course, the lack of food in some parts of the world isn't down to there not being enough of the stuff anyway. It's more a question of how the food we do have is distributed. You could also argue that in the west, where we are more concerned about obesity than starvation, the last thing we need is more food (although I am reliably informed they are very low in fat).
The somewhat unsavoury feast was accompanied by some interesting facts from host Jo Kessler, Stuart Hine, an entomologist at the museum, and Daniel Creedon, head chef at Archipelago, a London restaurant that counts various insects among the items on its menu.
According to the panel, insects are starting to catch on as a luxury foodstuff and can be bought in some of London's most well-heeled grocers. Archipelago is also a success story, and doesn't seem to have any problem attracting adventurous diners. The most popular item on the menu, says Daniel, is the "Love Bug Salad" which includes wok-fried locusts and crickets. And insects have apparently become popular enough to warrant attention from the UK's Food Standards Agency.
Back in 1855, Holt felt the working man should supplement his diet with various creepy-crawlies, dreaming up such delights as wireworm sauce and slug soup. We were, at least, spared those.