LIBRARY

THE ANATOMY OF INSECTS 23
pollen basket on the hind legs of bees. Pretarsus - in some insects a small distal
portion of the apical segment bearing the claws, pulvilli, or empodia.
Claws, tarsal claws, ungues - one or two curved, simple, toothed, or bifid
claws used chiefly for clinging to plants, animal hosts, and other objects; opposing
a tooth on the tibire in the ANOPLURA.
Pulvillus (pI. pulvilli) or onychium -- slender or pad-like cushions on the ventral
tarsal segments or a pair beneath the claws of DIPTERA; may be provided
with hollow tenant hairs for exuding adhesive secretions to aid in clinging to
surfaces.
Empodium (pI. empodia) - a small appendage between the apical pulvilli
and associated with the claws in DIPTERA.
Arolium (pI. aralia) - a pad-like appendage between the claws of orthopteraid
insects.
Wings. - Insects are apterous, brachypterous, or fully winged. There are
usually two pairs of wings: primary or fore pair and secondary or hind pair.
The primary wings arc usually considerably larger than the secondaries although
in a number of orders both pairs are nearly equal in size. In certain few
EPHEMERIDA there is but a single pair while in the DIPTERA the secondary
wings are represented by a pair of small capitate appendages or halteres,
commonly referred to as balancers or poisers. In the brachypterous forms the
wings are often shortened or stub-like. In various groups one or both sexes may
be either winged or apterous. In others the wings are atrophied or rudimentary.
The wings are bag-like membranous structures developed as lateral extensions
of the mesonotum and metanotum. They are articulated to the sides of
the notum by means of the anterior and posterior calli of the wing bases coupled
to the anterior and posterior axillaries of the notum, aided by the pleural wing
process beneath and the two paraptera, one on each side of the base. The axillary
membrane is attached to the base of the wing. It extends from the tegulre
to the axillary cord and surrounds the small axillaries or axillary sclerites referred
La above. The wings consist of a double membrane which may be smooth
and naked or covered with rnicrotrichia, minute fixed hairs, acutece, microscopic
microtrichia, or macrotrichia, larger movable hairs and scales. The otherwise
fragile organs of flight are traversed by trachere of the respiratory system and
strengthened by a simple or complicated system of veins or nerVI,lres which are
sclerotized arches on eithet membrane over the trachere or disposed longitudinally
in a system of branches or longitudinally and transversely into a fine or
coarse network. Alula (pI. alula;) or s(/uama (pI. squamce) - one or more membranous
lobes or scale-like expansions of the basal axillary membrane which fold
beneath the bases of the closed wings of COLEOPTERA and DIPTERA.
Aileron and alutet may be used in a similar sense, and calypter is employed when
these lobes Cover the halteres in DIPTERA.
Axillary excision - a notch near the base of the inner hind margin of the
wing which separates the small posterior or basal lobe from the rest of the wing.
Wing couplings. - The two pairs of insect wings are held together in flight
by various coupling devices. One of the commonest types consists of one or