306 TRANSFORMATIONS OF INSECTS. 
many species of the family have been used in the healing art 
ever since the time of Hippocrates and Areteus. The integu- 
ments of these insects contain the blistering substance, and as this 
is so much used a great deal of trouble has been taken to 
investigate their habits and metamorphoses, but without much 
SUCCESS. 
The oil beetles belong to this family, although they are 
apparently very differently formed to the brilliant blistering fly. 
These oil beetles, which belong to the genus JAZe/oé, emit an 
oily liquor like those just mentioned, and it has vesicating 
properties. The insects do not fly, they have no wings, and 
their elytra are very short, their bodies being clumsy, heavy, 
and soft. They crawl over low plants and grasses, and feed 
upon wild buttercups, and they are apt to be eaten by cattle, 
whose mouths soon become much affected. The metamorphoses 
of some of the Caztharide have been very ably investigated by 
George Newport and other naturalists. Thus, in the year 1700, 
Goedart collected the eggs of some species of JZe/oé, and ob- 
tained some young larve. Later De Geer did the same, but in 
both cases the larve perished immediately after their birth, and 
the observations of the two authors were forgotten. In 1802, 
Kirby, a celebrated English entomologist, found a small insect 
which resembled the larve described by Goedart and De Geer 
upon some A/ymenoptera related to the bees, and belonging to 
the genus Axdrena, or solitary bees. He thought they were 
parasites. In 1828 Leon Dufour found an insect which probably 
belonged to a parasite of the same kind as those just noticed. 
He considered it to be a new species, and he called it by the 
name of Z7iongulinus. Many observers managed to hatch the 
eggs of Melo’, Spanish flies, and of species of the genus S7¢a77s, 
which belongs to the same family, but does not possess blistering 
properties, but they did not get further than the point obtained 
by Goedart in the year 1700. After a time, however, it became 
evident that the young larve hooked themselves on, whenever 
they had the opportunity, to other insects provided with wings, 
and especially to the nest-making Mymenoptera; and Victor 
Audouin found some full grown and adult individuals of species 
of Szfaris in the nests of the solitary bees. There appeared, 
