69 
Whenever grasshoppers are numerous we shall soon find 
that blister-beetles increase in numbers, and as the adults 
have a very good appetite, but no grasshopper eggs, 
they destroy alarge amount of foliage. In my attempts 
to grow a number of foreign species of vetches for fod- 
der plants these beetles have been a great nuisance, as 
they would devour the leaves of such plants just about as fast 
as they appeared above ground, and only a thorough dusting 
with poison could save them. The beetle would find such vetches 
even if surrounded and almost covered and hidden by other 
plants. As blister-beetles are more or less gregarious they 
cause much injury to the plants they select for food. They 
seem to be very stupid, at least they do not use their wings as 
readily to escape as other insects, and being voracious feeders 
they can, if absolutely necessary, be killed by an application of 
Paris-green or London-purple, Yetif thedamage they cause 
is not. too great they should not be killed, because their off- 
spring are such great friends to the farmer, assisting him most 
effectually against the destructive grasshoppers. Nor can 
they multiply beyond a certain degree, even if the adults have 
ample food, because their larvae have to depend upon the num- 
ber of eggs deposited by the grasshoppers, and if this supply of 
eggs is small the resulting number of blister-beetles is also . 
small, 
These beetles have a peculiar life-history. The female de- 
posits a large number of eggs in a cavity in the soil. These 
eggs in hatching produce long-legged and very active larve, 
which run about like hunting dogs until they discover the 
whereabouts of the eggs of grasshoppers. Having discovered 
them the larva isnot slow to devour one or a few of them. 
This done it throws off its old skin, and being now surrounded 
by plenty of food the former useful long legs are no longer re- 
quired and they are replaced in the new skin by rudimentary 
ones. As these larvee destroy more eggs than they eat they are 
of course very beneficial, and blister-beetles, though them- 
selves very destructive, should be protected on account of their 
beneficial larvee. 
We have several species of such blister-beetles, but all have 
essentially the same habits. The illustration of the potato- 
beetle (Fig. 36, Plate 6,) shows also some adult blister-beetles. 
