The Spanish fly beetle is a type of bubble beetle.
Technically known as the blister beetle, the blister beetle is an insect that produces chemicals that can burn the skin and cause blisters. There are many different species of insects throughout the world. They generally feed on vegetative crops and can occur in large groups. The burning chemical, cantharidin, is poisonous to animals and acts as a deterrent to animals that might otherwise eat them.
Scientists classify animals and insects into groups based on how they are related to each other. Each insect in the bubble is of a particular species; for example, Epicuata vittata. Species groups then fall into genus groups such as Epicuata or Lytta. Collections of all genera, which is the plural of genus, belong to the family Meloidae.
More than 2,500 species of vesicles are included in the Meloidae family. Although beetles live all over the world, they all contain a chemical called cantharidin. Some insects only produce a pungent or poisonous chemical from specialized glands and release them only in certain situations, such as directly onto a would-be attacker.
A bubble bug does not deliberately release cantharidin. Instead, it contains the chemical within its body, passing through the insect’s tissues and blood. The presence of this vesicular substance is not helpful for an individual beetle, in the face of a predator that wants to eat it, or in a situation where the beetle is going to be crushed. However, throughout the evolution of the species, the unpleasant and dangerous burning of the chemical teaches animals and humans to avoid it. The species is then less likely to be eaten.
Sometimes, however, the beetles experience predation or crushing or accidental contact. When the adult is crushed, or a human, for example, touches it in a way that scares the beetle, the cantharidin leaves the body and burns the skin. Normally, adult beetles feed on plants and can be accidentally eaten by animals while grazing. Only a beetle is capable of killing an animal, and since cantharidin persists in the insect even after death, the beetle does not need to be alive to kill an animal.
Visually, a bubble bug has a cylinder-shaped body and an obvious neck between the body and the head. They come in a variety of colors, from dull brown to striped yellow. Insects often swarm where there is food. Adults are agricultural pests, but immature forms can be useful as pest controllers, eating grasshopper and cricket eggs.