14 USEFUL BIRDS. 
Most insects emerge from eggs, which ordinarily are de- 
posited and fixed by the female parent in positions where 
the young will find suitable food in readiness 
for them when the eggs hatch. Some insects 
bring forth their young alive, but this is an 
Fig. 5.—Fly ana exception to the general rule. The young 
itslarva. insect that emerges from the egg is called the 
larva (plural, larve). Some larve are provided with short 
legs or feet, others have none that can be seen ; but all are 
without wings, and move about mainly by crawling. Their 
principal occupation is to feed. Some species, such as the 
Fig. 6.— Chestnut beetle or weevil, enlarged. a, larva or grub, enlarged; 
b, young larva in chestnut, natural size. 
leaf-eating caterpillars, rest during certain parts of the day ; 
others, like the larve of fiesh-feeding flies, apparently feed 
constantly. As all eat enormously and grow rapidly, they 
are capable, when in great numbers, of doing much harm or 
good, as the case may be. The larve of flies are commonly 
called maggots or slugs, those of beetles are called grubs, 
and those of butterflies and moths are called caterpillars. 
Much of the injury 
done by insect pests 
is attributable to the 
Jarvee 3 a Ithou g h Fig. '7.— Caterpillars, the larvze of butterflies. 
idan 
some, like certain leaf-eating beetles, are injurious in the per- 
fect form. During the rapid growth of a larva the skin is 
shed several times, until full size is reached, when the next 
transformation is effected, and the larva becomes a pupa or 
chrysalis. Among the butterflies and moths (Lepidoptera) 
the insect often spins from within itself a thread, which it 
weaves into a case or cocoon which encloses it while in the 
