INSECTS. 123 
(Pzyelus) is common in the grass in early summer. When 
hatched, the young crawl up blades of grass, puncture 
them with their mouths, and suck the juice, a watery fluid 
escaping from various pores of the insect and completely 
covering it. To obtain air, its tail is thrust through the 
fluid (Fig. 150, a), seizing a bubble by means of claspers, 
that passes along beneath the abdomen, entering the spi- 
racles. After a time the liquid becomes filled with air, 
4, and assumes the frothy appearance familiar as frog- 
spittle, from which the perfect insect finally escapes. 
Bark-Lice 
(Coccida).—The 
bark-lice are mi- 
nute scale-like in- 
sects, the males 
alone having wings. 
The cochineal 
(Fig. 151) is a fa- 
miliar form of the 
family. ° 
VALUE.—Thecoch- 
ineal industry givesem- 
ployment to thousands 
of persons. From Coc- 
Cus StEMStS COMES Wax 5 
400,000 pounds have 
been obtained in a sin- 
gle year, and made into 
candles, etc. 
Fic. 151.—1, Cochineal insects on a branch of 
cactus; 2, female; 3, male. 
Plant-Lice (4/idz).—These insects (Fig. 152) have 
flask-shaped bodies and a three-jointed beak. They mul- 
tiply in a marvelous manner. Eggs are deposited by the 
impregnated female in the autumn that hatch in the spring, 
producing, as a rule, wingless forms, that in turn produce 
not eggs but living winged or wingless young, that in ten 
or eleven days produce others, and so on, so that the origi- 
