572 Insects. 
When the Mexicans have gathered the Cochineal In- 
sects, they put them into holes in the ground, where 
they kill them with boiling water, and afterwards dry 
them in the sun ; or they kill them by putting them 
into an oven, or laying them upon hot plates. From 
the various methods of killing them arise the different 
colours in which they appear when brought to us. 
While they are living, they seem to be sprinkled over 
with a white powder, which they lose when the boiling 
water is poured upon them, but preserve when killed in 
an oven. Those dried upon hot plates are the best. 
The quantity of Cochineal annually exported from 
Mexico and South America is said to be worth more than 
five hundred thousand pounds sterling — a vast sum to 
arise from so minute an insect ; and the present annual 
consumption of Cochineal in England has been esti- 
mated at about one hundred and fifty thousand pounds 
weight. The Mexicans think so highly of their trade 
in this insect, that the republic has adopted the nopal- 
tree as part of its arms. 
It is for dyeing scarlet that Cochineal is chiefly in 
demand ; but, although a peculiarly brilliant dye is now 
obtained from it, this substance gave only a dull crim- 
son colour until a chemist of the name of Kuster, who 
lived at Bow, near London, about the middle of the 
seventeenth century, discovered the art of preparing it 
with a solution of tin. Cochineal, if kept in a dry place, 
may be preserved without injury for a great length of 
time. An instance has been mentioned of some of this 
dye, one hundred and thirty years old, having been 
found to produce the same effect as though it had been 
perfectly fresh. 
THE PLANT LOUSE, OE GEEEN FLY. (Aphis.) 
The Aphides are sometimes viviparous, and at other 
times oviparous, according to the season of the year. 
