Brief Overview of Helicoverpa zea Anatomy

1
Brief Overview of Helicoverpa zea Anatomy
2nd Abdominal Segment
True legs
Head
Prolegs
Figure 1. In Helicoverpa zea, the head is
followed by 3 pairs of true legs. The second
abdominal segment is the second segment found
between the true legs and the prolegs. The true
legs are followed by 4 pairs of prolegs.
2
Labial salivary gland
Caterpillar head
gut
Dissecting probe
Figure 2. Removal of the labial salivary glands
from H. zea. The glands are removed through a
longitudinal incision on the ventral side of the
caterpillar. The long thin, transparent white
glands are being held up for view with a
dissecting probe.
3
Dissecting pin
Caterpillar head
Labial salivary gland (dyed blue)
Gut
Figure 3. Here the labial salivary glands have
been artificially dyed for easier viewing.
4
H. zea Labial Salivary Gland Extraction
A.
H. zea Healed Cuticle After Salivary Gland
Extraction
B.
Figure 4a. Labial salivary gland removal through
a small incision on the ventral side of the
second abdominal segment.
Figure 4b. The cuticle is folded back over and
allowed to heal
5
Caterpillar average body weights in grams
Figure 5. Helicoverpa zea caterpillar average
body weights after feeding on excised leaves from
non-wounded tomato plants or excised leaves from
previously wounded tomato plants. Tomato plants
were mechanically wounded with scissors 4 days
prior to excision and then fed to 1st instar
caterpillars. Caterpillars were allowed to feed
on tomato leaves for 6 days and were weighed.
The caterpillars then fed on a fresh set of
leaves from plants treated in the same manner,
but the leaves were excised from plants that were
wounded with scissors 10 days previously.
Different letters represent statistically
significant differences (t-test) between
treatments at P
caterpillars was determined for each treatment.
Bars indicate mean ? s.e..
6
70.0
60.0
A Mechanically wounded tomato treated with
saliva B Non-wounded tomato C Mechanically
wounded tomato treated with water
50.0
40.0
Caterpillar mass (mg)
30.0
20.0
10.0
0.0
A
B
C
Treatment
Figure 6. Three representative frequency
distributions in Dice-Leraas style where the
vertical line is the range of measurements for
the sample, the horizontal line is the mean
(arithmetic average, or X bar), and the
rectangles are 95 confidence intervals about
the mean. Comparing hypothetical treatments A, B,
and C, it is shown that the rectangle of
treatment A falls within the confidence rectangle
for treatment C indicating that the means of
treatment A and C are not significantly
different with a 95 degree of confidence. The
rectangle of treatment B does not fall within
the confidence rectangle for treatments A or C,
indicating with a 95 degree of confidence that B
is significantly different than treatments A and
C (Halpern, 2000).
7
Regurgitant
Figure 7. Slightly squeezing a caterpillar
abdomen between your finger tips will cause the
caterpillar to regurgitate as a fright response.
8
A
B

Figure 8. Wounded corn plants to illustrate how
plants can be wounded to for induced plant
defense experiments. (A) Helicoverpa zea corn
earworm/tomato fruit worm caterpillar feeding a
corn plant for an induced plant defense
experiment. (B) Hole punch has been used to
wound a corn plant to simulate insect herbivory
instead of scissors.