158 Bulletin 151, Truck and Garden Insects

 Like the last-named insect, this one is injurious only on
land that grew much grass during the preceding year. Eggs
are laid on grasses in low wet land, where alone bill-bug injury
is ever severe. The young feed chiefly on the roots of grasses, but
one species (S. robustus) may live in the pith of the corn stalk.
 The measures recommended for use against root webworms
 (page 156) are also the ones to be used against bill-bugs.
 CORN-LEAF BLOTCH-MINER (Agromyza parvicornis)
 This larva of a minute black fly makes irregular shaped
blotches in the leaves of corn and some grasses by eating the
tissue from between the lower and the upper epidermis. Its
injuries are most noticeable and serious on young corn. The egg
is laid in the corn leaf and hatches in 3 or 4 days in summer.
The larva feeds from 3 to 12 days in summer. It breeds during the
winter in southern Florida (J1. Agr. Research, April 12, 1916).
 The insect cannot be reached by any insecticide. The only
course is to pull up and destroy badly infested plants, and by
good care, keep the others in such a vigorously growing condi-
tion as to overcome the injury. An excess of corn should be
planted so that a good stand will remain after the requirements
of the flies have been met and the infested plants pulled up.
 SOUTHERN CORN ROOT-WORM (Diabrotica 12-punctata)
 This insect spends both its larval and adult stages on corn.


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The adult (fig. 84, a)
feeds on the leaves in
which it makes small
holes, but it is more
common on the silk of
the young ears which
it cuts off. It may at-
tack also the tassel or
the exposed kernels of
the ears. The white,
grub-like larvae (fig.
84, c) mine the roots
of the corn. The adult
beetles are oblong and
about 11/4 inches long,
red in color, with 12


black spots on the wing covers. The insects are more abundant on
late corn than on early varieties and apparently are more common
in the western part of the State than on the peninsula.


FIG. 84.-Southern corn root-worm: a, Adult beetle,
 about six times natural size; b, egg; c, larva; d,
 anal segment of larva; e, work of larva at base
 of corn stalk; f, pupa. (From U. S. Bur. of Ent.)