72 
Thus there are four moults, or five instars, and the mother does 
not reproduce until after the last moult. 
Another student (J. P. Gilbert) found five moults in one instance: 
an isolated female, born June 20, moulted June 23, 26, 27, 29, and 30. 
Each cast skin was removed as soon as found, and five of them were 
found. 
More interesting than the number of moults is the fact that the 
females reproduce for many successive generations without the aid of 
the male— -a normal phenomenon among aphids, and many other in- 
sects as well — and also the fact that the young are born alive. This 
can easily be witnessed, as aphids are so numerous. In this species 
the young aphid emerges hind end first and back upward, and envel- 
oped in a delicate membrane, which it gets rid of by means of vigorous 
kicking. The entire process, requiring ten or fifteen minutes, is essen- 
tially as described elsewhere and in more detail for other species. 
The mother does not wander much after beginning to reproduce, 
but stays in one spot, with the younger of her progeny clustered 
around her. 
The winged females, which may occur in any of the seventeen or 
more generations, are the chief means of spreading the s])ecies. They 
are feeble of flight, but are often assisted by the wind to reach distant 
places. 
Fertilization is evidently essential to the production of an egg 
that will hatch, tho eggs are laid whether fertilization has occurred or 
not. The deposition of an egg requires about seven minutes, as noted 
by E. O. G. Kelly, who observed also that the female used her hind 
legs to assist the egg out. A fluid that accompanies the egg serves to 
glue it to a green leaflet, on either side of which the egg may be laid. 
The eggs remain over winter on the dead leaves or stems on the 
ground. 
In November there are still many mature females in the field, and 
they feed on mild days, crawling under shelter when the weather turns 
cold. If clover sod is brought indoors during the winter, the females 
appear with the new growth and the plants soon become overrun with 
aphids. Out-of-doors, most of the hibernating females meet their 
death sooner or later during the winter, in this region, notwithstanding 
the fact, reported by W. G. Johnson, that the species can survive 
severe freezing. 
Natural Enemies. — The most important enemy of this louse is a 
common fungus, Empusa aphidis. It is wide-spread in the United States 
and Canada, and affects a great variety of aphids, its abundance, when 
it occurs, being proportional to that of its host. It does not appear in 
dry weather but is common after a rain or two at any time during the 
growing season, and is most abundant under the combined influences 
of moisture and warmth. Then it sweeps off myriads of aphids. 
Those killed by the epidemic remain clinging to the plant in a more or 
less lifelike attitude, but turn yellow and then light brown, become 
swollen, and evLMitually coated with the fungus ( I'l. III., T'^ig. 3). The 
