The vestigial locus seems to be mainly involved in
the development of the wing margin. The mutants are recessive
viable (with or without a visible phenotype), recessive
lethal, or dominant (with a visible phenotype over wild type
or a vg allele); some alleles complement each other; others
show pleotropic effects or homeosis (Bownes and Roberts,
1981). In the classical vg mutants, the wings of homozygotes
are reduced to vestiges and usually held at right angles to
the body, the wing veins still visible. Some mutants have
narrow, nicked, or scalloped wings. Halteres may be reduced
or absent. Postscutellar bristles are frequently held erect.
Viability is somewhat reduced; null mutants are sterile. Temperatures of 29 or greater appreciably increase wing size
(Harnly, 1936, Genetics 21: 84-103; Stanley, 1935, J. Exp.
Zool. 69: 459-95). A suppressor of vg on the third chromosome, su(vg), results in an almost normal phenotype at 28, an
intermediate vg phenotype at 25, and a strong vg phenotype (in
wings and especially halteres) under 20 (David, et al., 1970).
vg/+ heterozygotes with certain Minutes show scalloping of
the wings (Green and Oliver, 1940; Simpson et al., 1981).
vg/vg/+ has scalloped wings more often than vg/+ (Green,
1946). Final size of larva is smaller than in wild type and
pupation occurs slightly later. Wing disks of late larva are
also somewhat smaller than in wild type (Auerbach, 1936), as
are haltere disks (Chen, 1929). Goldschmidt (1935, 1937)
claimed that wings are more or less fully formed and subsequently eroded by degeneration during pupation. Waddington
(1939, 1940) found no evidence of erosion and concluded that
the effect of the gene occurs during the larval period and
involves reduction in size of prospective wing area and shift
in position of line along which wing area is folded out from
the imaginal disk. Fristrom (1968, 1969), however, using both
light and electron microscopy, found numerous degenerating
cells in the presumptive wing blade region of the vg wing
disks, as did Bryant and Girton (1980), Bownes and Roberts
(1981a, 1981b), James and Bryant (1981), and O'Brochta and
Bryant (1983). Duplications of the mesonotum along with deficiences of wing disk material occur in a small percentage of
vg mutants (Girton and Bryant, 1980; James and Bryant, 1981).