The state herald., 1908-07-03
THE GREEN BUG.

the attacks OF numbers Of predaceous
and parasitic enemies. Among tho
former are Syrphid flies. two.winged
Insects. which place their eggs among
the colonies. the eggs Matching into
hungry maggots which consume large
numbers of lice. The socalled lady
birds" beetles belonging to the family
Coccinellidae. do the same thing. their
grubs or young devouring enormous
numbers Of aphids.
Among their parasitic enemies tho
most prominent. In fact the parasite
through whose work In normal years
both ToSoptera and Macrosiphum arc
kept In check. is a small four.wlnged
hymenopterous insect, Lysiphlebus tri.
ticl which. upon the advent of warm
weather In the south last summer. rap
idly increased and reduced the hordes
OF lice. This insect we found In the
north. last summer, and reared II re-
peatedly from Toxoptera. Unfortun.
ately l.. trltlci does not reproduce
freely at low temperatures; below
sc degrees +. II is said to be Inactive.
or. as Webster puts 1t. II is active only
when the temperature is 90 degrees
above that Mt which the green bug
breeds freely. The method Of attack
on the part OF this parasite is shown
In Fig. OF one OF our Illustrations.
and represents an individual OF
Lysiphlebus sp. in the act Of oyiposit-
ing In specimen Of NJ. granaria.
Normally l.. tritici. as observed by us.
approaches ToNoptera very deliberate
ly, generally from behind. though fre.
quently from the front, and oylposits
with but little. or at least without cf-
fcctiye resistance on the part OF that
louse: but Macrosiphum appears to
be more on the defensive. and foo
requiring finer tactics. This may ne
count for the method of attack as
shown. The egg placed in tho body
Of tho louse. hatches In n few days.
Tho lnryn feeds upon the tissues OF It's
host. preventing. Il IL claimed. any
great production of young. and In this
way. even before the death OF It's host.
doing much 10 check tho Increase of
the pest. Later. about week from
Matching possibly the parasite has Mt.
tained It's full sire. and with IN. prop
or light and magnltcation. can be dis
tinFuishcd through the body wall OF
Its host. Fig. 3. Tho body Of the louss
hwollH. tho individual dies, the skin
dhrkena and hnrdens. and In short
time tho little parasite emorEcs an
fourwing.d fly from n round hole cut
In the abdominal wall Of the dead In.
sect. Fig. 4. prepared to mate and
cnrfy on the good work. n only tho
weather will permit. Millions Of thiH
genus Of parasites arc In our fields.
working not only upon Tosop,era.
when present. but upon some other
plant lice. notably Maofoaiphum. and
In ordinary years arc tho principal
means Of keeping these pests In
check. II ~ nm announcement to
know that young lice destined 10 bo
winged are frequently parsi,isnd:
hence. whom the image migrant flas To
other neldA. II froluonti, carries tho
beneficial insect with II. II n worthy
~ note also In connection with tho
subjects Of pafanitisn. that wo md In
the north climatic conditions which
afs directly opposed 10 any disastrous
outbreak Of grain plant lice, In other
words. We have cold winters and warm
summers. tho nrst factor preventing
any undue Increase Of lioo unattended
by parasi,ism. and tho warm SUM
rafs allowing Of a a rapid Increase
Of parasites before tho lice hayS
gaiasd much hssdway.