Tacos were originally made with bugs.

The indigenous tacos are of Charales, maguey worms, sweet water shrimps, ant spawn or escamoles, and even chapulines (a kind of crickets).

If you are lucky enough to live where people of Mexican extraction live, exotic items such as gusanos (worms) de maguey or chapulines might be available.

Insects were a major part of the pre-Columbian diet. Mexicans did not have many animal proteins to eat because they had so few farm animals. So insects were an important food. To this day, insects are served for food in many parts of the country. It is one of the ways Mexicans retain their food traditions.

The taco was created because the peasants were looking for a way in which their workers could take their lunches with them to the farmlands. As the cities grew, the peasant farmers took their taco habits to the cities. Soon the the fast food taco was one of the preferred meals of the Mexicans.

The main ingredient of the taco is the tortilla. It is filled with different stews and seasoned with tomato and chili sauces, vegetables, and some other ingredients.  Tacos are most often made with beef, pork, or chicken and sometimes lamb meat that is cooked in maguey sauce (worm sauce). The Mexican tacos are quick to cook and cheap to buy.

The tacos of canasta (basket) or sudados are from México City. They are sold in baskets, and made with small tortillas that are not rolled but bent. They often include green mole, pork meat in pipian, ground meat, and potatoes with smoked pork sausage.

The seafood tacos are filled with breaded shrimp, fried fish, and shellfish.

 

(adapted from source)