COLEOPTERA 495 



Family MEhOYDM 

 The Blister-Beetles 



The blister-beetles are of medium or large size. The body is com- 

 paratively soft; the head is broad, vertical, and abruptly narrowed 

 into a neck; the prothorax is narrower than the wing-covers, which 

 are soft and flexible ; the legs are long and slender ; the hind tarsi are 

 four-jointed, and the fore and middle tarsi are five-jointed. 



These beetles are found on foliage and on flowers, on which they 

 feed in the adult state; some of the species are very common on 

 goldenrod in the autumn; and several species feed on the leaves of 

 potato. 



The blister-beetles are so called because they are used for making 

 blister-plasters. The beetles are killed, dried, and pulverized, and 

 the powder thus obtained is made into a paste, which when applied 

 to the skin produces a blister. The species most commonly used is a 

 European one, comm.only known as the Spanish-fl}^; but our Ameri- 

 can species possess the same blistering property. 



The postembryonic development of those blister-beetles of which 

 the complete life-history is known is a very remarkable one; for it 

 has been found that in each of these cases there is a complicated 

 hypermetamorphosis. The food of the larva consists, in some species, 

 of the eggs of short-horned grasshoppers, in others of the egg and the 

 food stored in the cell of some solitary bee. The female blister-beetle 

 lays her eggs in the ground; a large number of eggs are laid by a 

 single female ; this fact is doubtless correlated with the difficulties to 

 be overcome by the lai-v^ in their search for their proper food, in 

 which comparatively few are successful. The newly hatched larva is 

 cimpodeiform (Fig. 587, A), and is known as the triungulin, a term 

 applied to the first instar of blister-beetle larvee. This term was sug- 

 gested by the fact that in this instar the tarsi appear to be three- 

 clawed; but in reality each tarsus is armed with a single claw, on each 

 side of which there is a claw-like seta. 



The triungulins are very active. In the case of those that feed 

 on the eggs of short-homed grasshoppers, they run over the ground 

 seeking a place where one of these insects has deposited its egg-pod; 

 if a triungulin is successful in this search it bores its way into the egg- 

 pod; if more than one find the same egg-pod, battles occur till only 

 one is left. In the case of those species that develop in the nests of 

 bees, the triimgulin, instead of hunting for a nest, merely climbs a 

 plant, and remains near a flower till it has a chance to seize hold of 

 a bee visiting the flower; it then clings to the bee until she goes to 

 her nest, then, letting go of the bee, it remains in the cell and is shut 

 up there with the egg of the bee and the store of food which she 

 provides for her yoimg. The triungulin first devours the egg; after 

 which it molts and undergoes a change of form, becoming a clumsy 

 creature, which feeds upon the food stored in the cell. Several other 

 changes in form occur before the beetle reaches the adult stage; these 

 changes are quite similar to those undergone by the larva cfEpzVatito, 

 described below. 



