LIBRARY

422
COLLEGE ENTOMOLOGY
Eyes -large, globular, or elongated; separated.
Ocelli - usually two, situated close behind the eyes; often concealed by
hairs and scales; or absent.
Mouth parts - suctorial; mandibulate in MICROPTERYGIDlE; with
prominent coiled proboscis. Clypeus - small or large median frontal
plate. Labrum - small, short or narrow triangular plate. Genre - narrow.
Mandibles - usually wholly absent or microscopically rudimentary.
Proboscis - formed by the modified galea of the maxillre, which are
greatly elongated wit.h a small semicircular longitudinal groove on inner
surface of each, superimposed and locked to form a sucking tube of three
channels; sometimes with denticIes at tips to puncture plant cells; ringed
and coiled like watch spring under thorax at rest; sometimes very long,
up to 20 in.; vestigial and functionless in certain moths; Maxillary palpi
- often prominent, five- to six-segmented when most fully developed;
folded (TINEID.tE and related families); absent, or abbreviated to t.wo or
three segments (NOCTUIDLE); one-segmented (SPHINGIDLE, GEOME­
TRIDJE, P APILIONIDJE). Labium - reduced to small plate. Labial
palpi - reduced or well developed, conspicuous, usually three-segmented
in butterflies. Hypopharynx present.
Thorax - well developed, segments fused; the venter being called the pectus.
Prothorax - normal in lower forms and reduced to a narrow collar in higher
groups; with patagia, or dorsa-lateral sclerites which are directed backwards,
well developed in some genera.
Mesothorax -largest. Metathorax - of same size or smaller than mesothorax,
with scaly posteriorly directed sclerites or tegula:; over the bases of
the primaries.
Wings (see also same in section on External Anatomy) - normally two
pairs, well developed; rarely vestigial and useless; fore pair or primaries
usually larger than the second pair or secondaries; membranous, clothed
with hairs and overlapping scales, and also macrotrichia (and rarely microtrichia)
or minute hairs, and androconia or gland scales in some males
(PIER IDlE and NYMPHALIDJE); veins strong, many longitudinal and
few cross veins, branching, venation similar in primaries and secondaries
in some forms, different in most families; usually held erect, horizontally,
or roof-like at rest. Scales - variable in form, thin and flat hollow sacs
strengthened by minute strire and with short pointed pedicel engaging
minute puncture in wing membrane; plain, striated, often iridescent and
beautiful. They occur in quantities in plankton, indicating that they are
scattered far and wide by the butterflies and moths. Wing couplings that
hold the two pairs of wings together in flight are: jugum (jugal lobe), a lobe
supporting a number of sensory bristles on the anal area of the primaries,
projecting backwards to engage the frenulum; frenulum (humeral lobe),
a lobe bearing sensory bristles on the humeral angle of the secondaries,
projecting forward to engage the jugum; or strong chitinous hooks on the
subcostal vein of the secondaries in certain males and fewer females which