LIBRARY

18
COLLEGE ENTOMOLOGY
Mouth Parts. - The most important organs of the head, the mouth parts,
present many specializations in form and development and are always c1illicult
for beginning students to comprehend. As a matter of fact, a comprehensive
comparative study of the various organs may require a lifetime. While there is
great specialization in certain groups, at least two types are more or less easily
recognized in their simple outward forms. The most generalized is the mandibu.
late or biting type which forms the basis with which all others are compared.
FIG. 10. Biting mouth parts of the caterpillar of the European cabbage butterfly, Pieris
brassiere (Linn.). (After Pfurtschcllcr.)
Little is to be discovered from the exterior, but when a careful examination is
undertaken, the position, form, and structure of the important parts and their
appendages are simple enough. Those of the grasshopper are typical and usually
selected for the purpose. The removal for study is best accomplished as indicated
in Fig. 9, and the separate parts are illustrated in practically every en.
tomological text.
Labrum or upper lip - the front terminal head sclerite, hinged to the c1ypeusj
variable in size and shape; oval, rectangular, triangular, or linear; dorsal cover- ..
ing of the buccal cavity.
Mandibles or true jaws - paired, strongly sclerotized, piercing, biting, and
chewing organs; variable in size and shape: stYlet-like (flies, fleas), sickleshaped
and grooved (lacewings, beetJes), formidable organs of defense (ter"
mites. beetles, ants), grotesqUely enlarged (stag beetles), greatly reduced (but.
terflies, moths), absent (certain caddis flies, flies, butterflies). They articulate
laterally and move inward to meet in the middle. In phytophagous forms the