136 
very useful for clear liquids, but is lable to become clogged 
with heavy ones, such as Bordeaux mixture. 
All spraying machinery should be carefully cleaned after 
use. With good care an outfit may be made to last for many 
years, but if neglected it soon becomes useless. The formulee 
for using Paris-green and London-purple are given in the 
article on potato-bugs, and the formula for kerosene-emulsion 
is given in the article on leaf-lice. 
THE APPLICATION OF DRY INSECTICIDES. 
Although usually less economical, it is sometimes desirable to 
dust plants with dry insecticides. Thisis done in many ways. 
The old way was to tie up the insecticide mixed with plaster, 
flour, air-slaked lime or some such powder, ina muslin sack, and 
to shake this over the plants to be poisoned. This is a very con- 
venient and efficient method when only a few plants are to 
be dusted. For applying dry poisons on a large scale, vari- 
ous appliances have been devised. The powder-bellows is a 
simple arrangement by means of which a blast of air from 
the bellows is made to carry the dust-like insecticide to the 
place for which it is intended. Another device for the same 
purpose is the Orchard-gun. In it asmall fan, about four inches 
in diameter, is driven very rapidly by means of crank and 
multiplying gears so arranged that one revolution of the crank 
gives thirty revolutions of the fan. In front of this fan is an 
arrangement for sifting the powder into the current of air, ° 
thus charging the blast with the insecticide which is carried 
along with it and discharged in a smoky cloud which settles 
on the foliage. It is always best to apply dust when the 
dew is on the plants, or just after a rain, as moisture is 
required to hold the poison to the foliage; otherwise the first 
wind will blow it away. It isnever safe to use dry insecticides 
near pastures or where itis liable to be blown onto the food of 
cattle or horses. 
CUT-WORMS.* 
The term cut-worm applies to caterpillars which have the 
injurious habit of cutting off or cutting into the food plants, so 
as to wilt or kill them. Usually this takes place in the early 
spring, and only very seldom later in the season. This pecu- 
* The illustration, Fig. 76, Plate 11, shows a number of our common cut-worms. 
