THE TOMATO OR TOBACCO WORM
[Illustration: Egg of Tomato worm moth enlarged.]
This insect is often very destructive to tomatoes and tobacco. Most
country boys and girls know it and fear its ugly looking horn. When full
grown it is four inches long, usually dark green with a number of
slanting white lines along either side. It is so near the color of the
plants that it is difficult to see it.
[Illustration: Young tomato worm.]
During the summer months the worms are common, being most abundant in
August. In the fall the mature worms go into the ground and change from
the worm to a large, oval, brown pupa with a jug-handle-like appendage
on the under side. These are often turned up when the garden is plowed
in the spring. After tomato plants are well started the large greyish
humming-bird-like moths comes from the ground and begin laying eggs. The
moth expands from four to six inches and is often seen at dusk visiting
the blossoms of "jimson weed" and other large tube flowers. They are
also found around lights at night.
Where they are troublesome the plants should either be sprayed with a
poison when the injury is first noticed or else the worms should be
picked off and destroyed. There is a small parasitic wasp which is very
helpful in destroying this caterpillar. They live inside the worm and
when mature bore out through the skin on the sides and back where they
spin small white egg-like cocoons from which later the small wasps
emerge. Often a hundred or more may come out of one worm.
STUDY AND OBSERVATION
Observe the worms where they are at work on tomatoes. Disturb them and
hear them grind their jaws together. Do they eat the foliage rapidly?
Dust a little Paris green on the foliage where a worm is eating and see
what happens in half an hour. Collect a number of the worms in a glass
fruit can and give them tomato leaves to eat and watch them grow. How
many segments are there to the body? How many of the segments have
small black spots on either side? These are holes through which the worm
breathes. Is the horn at the end of the body stiff enough to stick into
your hand? This is thought to be a sting but it is only an ornament and
is entirely harmless. When full grown they will burrow into the sand in
the jar and change to the pupa.
[Illustration: Full-fed tomato worm slightly reduced.]
[Illustration: Chrysalis or pupa of tomato worm. Note the
jug-handle-like sheaths enclosing the proboscis.]
Examine the brown pupa carefully and see if it can move. What is the
peculiar structure on the under side of the body? The moth which comes
from this in the spring is very large. It is covered with white and
black scales and hairs which give it a mottled appearance. Examine on
the under side of the head for a peculiar structure like a watch spring.
This is the sucking tube used in drawing up nectar from deep tubular
blossoms. When the moths are sipping nectar from "jimson weed" blossoms
they can be killed by pouring a little poison down into the blossoms.
[Illustration: Tomato worm moth natural size.]