LIBRARY

522
COLLEGE ENTOMOLOGY
thorax. The coxal cavities assume the shape of the base of the coxre which
fit into them. They are said to be open when they form the margin of the
thoracic segments. In all the ADEPHAGA, excepting the family CUPE­
SIDLE, they extend across and divide the first abdominal segment and
are said to be open behind. The presence of a trochantin, on the outer or
basal part of the divided trochanter, is also used.
5. 'Tarsal Segments: Normally the members of this order have five-segmented
tarsi. The segments may be similar or variable in size and shape. In
certain groups the first segment is very small and inconspicuous while in
others the fourth is so small as to be hidden and therefore easily overlooked.
Frequently a number of segments may be greatly widened and
pad-like, a condition commonly found in the fore tarsi of males. The last
segment is usually long and somewhat slender but may even be the largest.
The tarsal formulre, beginning with the anterior legs, may be constituted
as follows; 5-5-5 (five in each of the three pairs of legs, or pentamerous);
5-5-4 (heteromerous); 4--4-4 (tetramerous); 3-3-3 (trimerous).
SUMMARY OF IMPORTANT ADULT CHARACTERS -EXTERNAL ANATOMY
Size 1 - minute (0.25 mm.) to large (150 mm. long).
Shape - variable, elongate-oval, slender and robust, cylindrical, flattened,
or even larviform in some females.
Exoskeleton - usually hard, or leathery and elastic; smooth and shiny or dull
and clothed with hairs, scales, or spines; variously sculptured, striated, and
punctured; and ornamented with chitinous horns, tubercles, and other outgrowths.
Coloration - forms occurring in temperate and cold regions usually black,
brown, yellowish, or reddish - a few metallic and brightly colored forms
present. Bright colors are associated with diurnal habits (cicindelids, buprestids,
chrysomelids, cIerids, flower-loving cerambycids, etc.) Tropical forms
may be brilliantly colored, many being metallic and others enameled. They
are among the most beautiful objects in nature. Portions of the bodies have
been used in the arts as jewels in all parts of the world.
Head - prognathous and hypognathous; free; rarely with a basal constriction
or neck; normal or prolonged into a snout in the weevils.
Eyes - large, well developed, round, elongated, irregular, or rarely divided;
finely or coarsely facetted; variously placed on the head; absent in certain
cave-dwelling species and ectoparasites.
Ocelli - usually absent; a single frontal ocellus or a pair among the
ST APHYLINIDlE and DERMESTIDLE. Usually present in the larvre.
Antennre - exceedingly variable in size and shape; normally 10- or ll-seg-
I The sI?allest species are to be f?und in the family TRICHOPTERYGIDJE or fungus
beeUes whIch vary from 0.25-2 mm. m length. whereas the largest and bulkiest beetles are the
South American giants in the families CETONllDJE and DYNASTIDJE which may attain
a length of 150 mm. to the end of the horn.