LIBRARY

524.
COLLEGE ENTOMOLOGY
and may function as an ovipositor. Male genitalia - concealed within the
abdomen and exserted between stcrnites 9 and 10.
Sexual dimorphism - well developed in many species and characterized by
marked differences in size, color, and external anatomical characteristics.
Some of the latter may be summarized as follows:
Male
1. Large horn-like mandibles.
&. Greatly developed antennre
0. Pectinate
0. Lamellate.
3. Fore tarsi enlarged,
certain aquatic forms with suckers.
4. Longer legs.
Female
1. Often larger size.
2. Reduced antennre.
3. Enlarged tibire in fossorial forms.
4. Change in form
a. Larviform
b. Disk-like
c. Trilobite.
SUMMARY OF IMPORTANT ADULT CHARACTERS -INTERNAL ANATOMY
These characters are far too complicated and varied to permit more than the
simplest statements.
Digestive System.
Mouth - well developed in herbivores and little more than a receptacle to
receive the liquids at the bases of the mandibles in predacious forms.
Pharynx - the seat of the organs of taste in the epipharynx.
(Esophagus - simple tube of variable size.
Crop - enlargement of the posterior portion of the cesophagus; absent in
some genera and very large in others.
Proventriculus or gizzard - small chamber with chitinized or horny ridges
and teeth fully developed, particularly in the predators and wood eaters
- not so pronounced in the others.
MM-intestine - tubular, long to short; sac-like; convoluted, coiled, with
gastric creca present - sometimes in series.
Hind intestine - short to long, small or large, usually convoluted, with or
without creca. Colon or bladder-like crecum may be present in certain
genera.
Rectal papiUre - rarely present .
. Malpighian tubes - four to six.
Salivary glands - absent or present.
Silk glands - present in CHRYSOMELIDlE, CURCULIONIDlE, and
other families; fluid secreted by Malpighian tubes and taken from the
anus with the mouth. Used in making cocoons.
Rectal glands - paired organs opening near the anus; secreting odorous,
fetid, and offensive fluids used in self defense; sometimes expelled with
explosive force.
Circulatory System.
Dorsal vessel with variable number of chambers. Aorta extends through
thorax into the head and is branched at apex.