4 Farmers’ Bulletin 1128. 
APHIDS IN GENERAL. 
Aphids, or insects of the family Aphididae, have a development 
which is remarkable in several ways. Eggs laid in the autumn hatch 
in the spring about the time when vegetation revives. From these 
winter eggs is produced a generation of females, usually wingless, 
which reproduce without the intervention of males (agamic repro- 
duction), many species giving birth to living young. The adult 
aphids of this first generation are termed stem-mothers. The off- 
spring of the stem-mothers (second generation) may be winged or 
wingless, or both forms may occur. They reproduce without the 
intervention of males, some species being oviparous, or egg laying, 
and depositing eggs which do not require fertilization for develop- 
ment, while others are viviparous—that is, they bring forth young alive, 
the eggs developing and hatching within the body of the parent. 
A succession of generations may be produced in this way until the 
approach of autumn, when the true sexes appear and the females 
deposit eggs; or a species perhaps may be more or less biennial, some 
individuals producing true sexes only every second year. In still 
other species, the true sexes of which are at present unknown, reproduc- 
tion without the intervention of males continues for a series of years. 
The same species of aphid usually exhibits several forms, as wing- 
less agamic females, winged agamic females, and the true sexual 
forms. In thelast the male may be winged and the female wingless, or 
bothsexesmay bewingless. The different generations of agiven species 
may vary more or less in appearance, and in some instances this is the 
case to such an extent that they appear to belong to distinct species. 
Aphids feed upon sap which is sucked up through a beak pushed 
down into the tissues of the plant. Their presence on plants fre-. 
quently is indicated by a curled and distorted condition of foliage, 
though this is not always so. When the insects are abundant the 
drain upon the plant is very great, interfering with its proper growth 
and development, and in extreme cases causing the death of infested 
parts. The leaves and shoots of plants infested by aphids are fre- 
quently seen to be covered with a black substance, as if dusted with 
soot. This is due to a black fungus which grows on the “honeydew” 
excreted by the aphids and is not especially injurious, though often 
objectionable as marring the appearance of the plants and fruit. 
Honeydew may be produced in such quantities as to coat the leaves 
and is attractive to various species of ants and wasps, which are 
DESCRIPTION OF PLATE I. 
THE Rosy APPLE ApuHIs: A, Infested leaves and young apples, showing characteristic curling of the 
leaves; B, apples at later stage dwarfed and distorted by earlier attack of the aphids; C, mature aphid 
of first generation, pink variety; D, winged spring migrants going from apple to narrow-leaved plantain (£); 
E, narrow-leaved plantain infested by summer wingless generations; F, mature wingless summer aphid 
on plantain; G, fall migrants and males flying from plantain back to apple in fall; H, fall migrants and 
males alighting on apple leaves, the former giying birth to sexual females; J, a fall migrant; J, male; 
K, sexual female and eggs, the latter yellow at first, later turn black; L, twig showing the eggs in winter, 
