The Shiny Metal Blister Beetles

Among our common injurious insects we find the blister-beetle family. They are remarkable on account of the greater number of changes that they undergo during their life compared to the usual metamorphosis of most beetles. Blister beetles are soft-bodied, slender-legged insects of medium or large size, with broad heads and narrow thoraxes, and are usually slender in form. They vary in colors from gray, black or brown to bright metallic shades of red, blue, green or yellow. All of them are vegetable feeders in the adult stage, their food consisting of the leaves, flower petals, or pollen of various species of plants. Our most common and destructive species in the East, belonging to the genus Epicauta, does considerable damage in our gardens.

A yellow and black-striped form is known as the "old-fashioned potato beetle." The "margined blister beetle," is also known to attack potatoes, and completely defoliates the plants in certain areas. They also feed on the foliage of beets, tomatoes, and especially clematis. This species is grayish-black in color, always with the margins of the wing covers gray. It measures about five-eighths of an inch in length. One of our most common species is the black blister beetle that occurs very commonly on goldenrod.But all this has nothing to do with the name "blister beetle," which was given to it on account of its peculiar physiological properties. A substance called "cantharidin" is found to a greater or less extent in the bodies of nearly all members of the family. This substance when applied to the skin causes an inflammatory, or blistering effect. To utilize this property the beetles are dried and pulverized, and the powder thus obtained is made use of in medicine. The beetles in general use for this purpose come from Spain and other European countries, and are known under the name of "Spanish fly." Returning to the remarkable life history, we find that the adult females deposit large numbers of eggs on the ground or on plants, depending on the species of blister beetles concerned.

These eggs hatch into very long-legged larvae that run about in search of food. Some of these active youngsters find the eggs of grasshoppers upon which they feed. According to statistics, however, even this habit is of questionable value, as they also destroy other more valuable parasites of the grasshopper eggs. Other species of these slender-legged blister beetle larva find a situation where they watch for bees. When the right one comes along, they attach themselves to the hairy body, and are carried home by the unsuspecting bee to her nest. Here the young blister beetle after stealing the ride, makes itself at home in the bee's nest, and proceeds to devour the bee eggs and larvae, and finally the accumulated stores that were provided for the young bees. During this time the blister beetle has completed its own complicated life cycle, has transformed completely, and instead of the bee an adult beetle will emerge.