THE INSECT WORLD. 



235 



spots. They are often bred by bird-fanciers in large numbers, 

 and only need plenty of food to multiply rapidly. They rarely 

 do serious injury, but are not pleasant to have around, and may 

 be easily controlled by cleanliness, supplemented in extreme 

 cases with bisulphide of carbon. A few other small, brown 

 forms, among which the species of Triboliiun may be mentioned, 

 occur under like circumstances, but are amenable to the same 

 treatment. 



Fig. 226. 



Tyibolhim cou/usum.—a, adult ; b, larva ; c, pupa : e, head, with antenna ; f, same of 



T.JOrugiiieiim. 



Perhaps the most interesting, and economically the most im- 

 portant of this series, are the "blister-beetles," or Mcloidee. 

 The name ' ' blister-beetles' ' is from a peculiar property possessed 

 by them of raising blisters on the human skin. This is due to a 

 substance called " cantharidin," found in the juices of all the 

 species to a greater or less extent. The species generally used 

 in medicine comes from Spain, hence the insects are also known 

 as "Spanish flies." The beetles are rather soft-bodied, with 

 broad heads, the antennae often knotted in the males, the thorax 

 narrow and cylindrical, the wing-covers extending well down the 

 sides. Some of the species are brightly colored and banded, 

 occasionally metallic bronze or coppery, and all of them are leaf- 

 feeders. Among the common eastern species several attack 

 potatoes, and of these a yellow and black-striped form, Epicauta 

 vittata, is known as the "old-fashioned potato-bug." Asters 



15 



