LIBRARY

622
COLLEGE ENTOMOLOGY
anterior scutoprescutum and posterior scutellum; parapsides, tegula!, and
axilla! are lateral sc1erites in certain forms.
Metathorax - somewhat smaller and fused with the propodeum or first
abdominal segment in the suborder APOCRIT A (the fused thorax and
propodeum is known as the alitrunk); phragmata or endotergites (apodemes)
are often pronounced.
Wings - absent, atrophied, or well developed; two pairs, fore pair much
larger than hind pair; relatively narrow; stiff and membranous; naked
or with microtrichia; coupled by means of hamuli or hooks of hind wing
which engage a fold near the median posterior margin of the fore wing,
hamuli in series in a row of only two or three, or wholly absent; folded
fiat over the back at rest; prominent stigma or pterostigma in the fore
wings of many species. Venation - highly specialized, mostly by reduction
and fusion; with few longitudinal and cross veins, with a single
vein in the subcostal region of the fore pair which is absent in the hind
pair; and veins may be entirely absent in both pairs. There are anum·
ber of systems of wing venation, the three most important being (1) the
Old or lurinian System devised by the French entomologist L. Jurine
in 1820, (2) the Comslock-Needham System, 1898-1899 (see also Com·
stock 1918), and (3) the New or European System now generally used
in Europe. Tillyard (1926, p. 258) compares and discusses these systems.
Wings absent in both sexes of a few species of DIAPRIlDlE and
ICHNEUMONIDlE. Females apterous in all workers and some sexuales
in FORMICIDlE, in all MUTILLIDlE, MYRMOSIDlE, and THYN­
NIDlE, and frequently in the BRACONIDlE and ICHNEUMON IDlE.
Males apterous in certain FORMICIDLE and CALLIMOMIDlE.
Legs - usually slender and well formed; the three pairs similar; variable in
length and structure for running, jumping, nest building, digging, carrying
pollen, and grasping and holding prey. Trochanters - simple or
two-segmented in certain parasitic forms. Femora -large and strong
and greatly thickened in certain jumping chalcid flies and other groups.
Calcar or spur is a plOminent feature at the apex of the fore tibire in a
number of species and acts with a toothed invagination of the base of the
tarsus as a comb or strigiUs to clean the antennre. In most nectar· and
pollen-gathering bees the posterior tibia is dilated and furnished with
special hairs to act as a pollen basket or corbicula and the metatarsus is
flattened and studded with short stiff bristles on the inner side which
form a brush or scopa used for removing pollen from the body to the
pollen basket. Large specialized spurs may also occur on the hind tibire.
Tarsi - normally five-segmented; rarely two" or three-segmented in
certain parasites. Metatarsus of hind legs may be greatly enlarged and
widened in pollen-gathering bees. Two simple or dentate claws and a
single empodium present.
Spiracles - a pair present on the membrane between the pro- and mesothorax.
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