The newspaper., 1908-01-31
PARASITES VS.. WHITE GRUB.
What Illinois Expert Has Discovered
Concerning Work of Former.

The Illinois state entomologist, DR..
S. A. Forbes. of Urbana. has done
much in studying the parasites that
destroy the white grub. and the fol-
lowing items from his Office indicate
something of the beginning that has
been made in solving one of the vital
and urgent problems of the farmer.
The common grub wasp (Tiphia) is
much the most important insect enc
my of the white grub. 1t is a slender.
jet-black insect, usually two-thirds of
an inch long, with wings either clear
or tinged with dusky yellow.
1t enters the ground in search of the
grubs, follows them up in their bur-
rows and lays on the back of each
grub single egg. which matches into
footless maggot-like larva which ad-
heres to the surface of the grub, pune
lures its skin. and sucks its blood for
a time, but finally eats it up.
These maggots have been known to
destroy. under favorable circum-
stances, the entire grub population of
a badly infested field. The method of
this insect and the main facts of its
life history have been worked out in
DIR. Rorbes' insectary the past two
years by j. ]. Davis and ]. A. West.
from cocoons and infested grubs sent
in by E. o. G. Kelly from fields at Ell
licott. Ill.
The wasp attacks the grub and a
violent struggle ensues until the for
mer stings her prey. temporarily
paralyzing it. and then smears viscid
fluid upon the back of the grub not
far behind the head. and deposits her
egg on this sticky surface.
The operation occupies several min
utes and has been fully observed a
number of times. Several white grubs
found in the field had these parasites
on the under side of the body between
the thoracic legs.
The egg hatches in seven to ten
days and IL takes the maggot about
two weeks TO get its full growth. 1t
doubles its size the last two days.
when 1t devours the body of its host.
The full-grown maggot is two-thirds
to four-fifths of an inch In length.
In several cases an abundance OF its
cocoons were found in the ground, in
dicating an enormous destruction of
white grubs. No doubt this wasp is
an important agent in checking de
structive uprisings OF grubs.
A little tachinir fly is another para
site Of the grub. The adult is a largo
blackish-gray fy with general
resemblance to the common large
blow fly. Another parasite is the
young of a large. slendcr-bodied. dark
red ichneumon fly. Still another is &
bee-hy covered with erect yellow fur.
Mr.. West discovered May-beetles
dropping to earth trying to rid them
selves OF adult flies that were clinging
to them and apparently thrusting eggs
into their backs. The effect was tested
in breeding-cages. The beetles so
treated lived for some days and then
began to die. dipterous maggots being
found in the body. These flies were
also seen among the May-beetles on
the trees at night.
Nothing has been done to test the
possibility OF collecting and distribut-
ing parasites. other than those of con
tagious diseases. and the latter subject
has not been worked out to final con
clusions. So It is seen that the para
sites alone offer a large field for in
vestigation with a view to the destruc-
tion of white grubs.