104 
. HOP APHIS. 
Phorodon humuli Schr. 
UNAFFECTED Hop PLant.—A spray of hops, modeled in wax, representing the 
plant as it appears in vigorous growing condition and free from the attacks of its 
principal enemy, the hop aphis. This is to call attention to the stronger foliage and 
the more abundant and larger hops produced by plants from which the hop aphis 
has been eradicated by the use of proper remedies. 
AFFECTED Hop PLant.—<A spray of hops, modeled in wax, representing the vine 
as it appears when attacked by the hop aphis, showing the blackening and dis- 
coloration of the leaves and the small and inferior hops, which are also discolored 
and otherwise unsuitable for market. 
Winter Eces.—Enlarged model of the winter eggs, which are attached by the 
sexual female to the terminal twigs of the plum, in crevices around the buds. 
Srem-MorHer.—The stout female aphis shown in this enlarged model hatches 
from the winter egg and is characterized by shorter legs and honey-tubes. It gives 
birth, without the intervention of the male, to living young, of which three genera- 
tions are produced on the plum trees, the last being winged and migrating to the hop. 
Wincep Micrant.—This enlarged model represents the first winged generation, 
the third produced on the plum. It instinctively flies to the hop plantand is the 
progenitor of from five to twelve wingless generations of virgin females, which infest 
the hop plants until autumn and are the sole forms which depredate on the hop. 
In autumn the last generation again produces winged females which fly to the plum 
trees. 
Hop-AFrFrectine StaGe.—This enlarged model represents the structure and appear- 
ance of the five to twelve wingless cenerations of virgin females which people the 
hop plant until autumn. These are the progeny of the wv inged migrants and are the 
sole forms which injure the hop. 
Return Micrant.—This enlarged model represents the last generation produced 
on the hop, the winged migrant form which in September returns again to the plum 
and gives birth to three or more young, which are the true sexual females, the first 
perfect sexual females produced in the cycle up to this point. 
Pupa oF ReturN Micrant.—This model represents the pupal stage of the return 
migrant. The striking features are the wing pads, which with another molt become 
the ample flight organs seen in the model of the adult. 
TruE SeExuaL FemaLe.—This enlarged model represents the generation born of the 
return migrant, which never acquire wings and never leave the plum tree. Maturing 
in a few days, according to the temperature, they are fertilized by the true winged . 
males which have been subsequently developed on the hopsand have come from the 
hop fields to the plum. Shortly after fertilization the winter eggs, like those with 
which the cycle started, are deposited. 
Youne Sexual Femaie.—This enlarged model represents the newly hatched stage 
of the only perfectly developed sexual female produced in the life cycle of this 
insect. 
WincEep Matre.—This enlarged model represents the first and only male genera- 
tion produced in the life cycle of the hop aphis. This is developed in the autumn 
and flies from the hop to the plum and fertilizes the true sexual females. 
CHINCH BUG. 
Blissus leucopterus Say. 
THE Ecas.—This enlarged model represents the form of the egg and the terminal 
cap. The eggs are three- hundredths of an inch long, the top being squarely docked 
and surrounded by four round tubercles near the center. Color from pale whitish 
to amber. 
First Larvat Stace.—This stage, represented enlarged in this model, differs from | 
the adult in being more elongate and in having two-jointed tarsi, the head broader 
and more rounded and the joints of the body subequal. The prevailing color of the 
whole body is red. 
Seconp Laryat Stace.—After the first molt the form represented in this enlarged 
model is assumed. The red-becomes a brilliant vermilion and contrasts with the pale 
band across the middle of the body, while the head and prothorax are dusky and 
coriaceous. Two broad marks appear on the mesothorax and the second, fourth, 
and fifth abdominal sutures, and one at the tip of the abdomen. 
Pupa.—The pupa shown in this enlarged model approaches still more nearly the | 
form of the adult, and is not unlike the last larval stage except in being darker and — 
in the appearance of wing pads, which extend almost across the pale basal abdominal ‘ 
joints. 
