INSECT PESTS OF CIGAR-TYPE TOBACCOS 17 
larval period is about 3 weeks, and full-grown larvae attain an aver- 
age length of approximately 314 inches. “They are usually green with 
seven oblique black and white stripes on the sides, and the posterior 
end of the body bears a short red horn, from which the name “horn- 
worm” is derived (fig. 20, 2). It is only in this stage that the horn- 
worm is harmful to tobacco. The larva feeds on the leaves con- 
tinuously, with the exception of about four periods during the develop- 
ment of the larva, of about 24 hours duration each, when the skin is 
being shed. The rate of growth and the amount of food consumed 
increase rapidly during the latter part of the larval period. Thus it 
is desirable to destroy the worms in the early part of their develop- 
ment. When fully grown the larva enters the soil and changes to 
the pupa. 
FIGURE 20.— Life stages of the tobacco hornworm: A, Adult; 6b, larva, or cater- 
pillar; C, pupa. All about three-fourths natural size. 
The pupa, or resting stage, is spent at a depth of about 514 inches 
below the surface of the eround. This stage may require only about 
2 or 3 weeks during the summer. Considerable variation occurs, how- 
ever, and even at ‘this time of the year many larvae may enter the 
eround to remain in the pupal condition until the following season 
before changing into the adult form. Observations also indicate that 
the pupal stage may require almost 2 years in some instances. The 
pupa (fig. 20, C ) is brown and about 2 inches long. 
The adult of the tobacco hornworm 1s a large ‘brownish- gray moth 
(fig. 20, 4) with a wing spread of about 414 inches. The - forewings 
have a mottled appearance and each bears a small white spot near its 
center. The hind wings are darker and are marked by a number of 
AD a52 4) =: 
