30 : Farmers’ Bulletin 1128. . 
worts, hedge-nettles, and related plants. Here colonies develop 
during the summer, augmented by winged forms produced in other 
generations on the currants. The wingless ones remain upon the cur- 
rants and continue reproduction. In each generation some winged 
forms occur, but wingless individuals are present until late in July 
upon the bushes. In fact, occasional colonies remain throughout the 
summer. In the fall, during early October, migrants return to the 
currant bushes and deposit the sexual females. These wher mature 
are fertilized by the winged males and the eggs are laid upon the twigs. _ 
THE SOW-THISTLE APHIS.! 
The sow-thistle aphis is at times quite as abundant on currants as 
is the currant aphis. It is somewhat similar in color but can be dis- 
tinguished at once from the currant aphis by the swollen honey 
tubes. (Fig. 23, c.) In the currant aphis these are long and very 
slender. (Fig. 23, a.) The eggs are polished black. The sow- 
thistle aphis injures the currant in about the same way as does the 
currant aphis, though the infested leaves (fig. 23, d) do not take on 
a reddish coloration. 
SEASONAL HISTORY. 
The seasonal history of this species upon currants is very similar to 
that of the currant aphis. The winged forms, however, migrate to 
the sow thistle and upon this they reproduce. After the production 
of numerous generations here during the summer, fall migrants are 
developed which return to the currants. Egg-laying females are 
then produced and these are fertilized by the winged males. The 
eggs are laid upon the twigs at about the same time as those of the 
currant aphis. 
THE GREEN CURRANT APHIS.’ 
A species which may be called the green currant aphis has for 
years occurred with the currant aphis, which it resembles 
closely. The wingless forms of the present species are green, whereas 
those of the currant aphis are yellowish. The life history, so far as 
is known, is very like that of the currant aphis and the two forms 
often may be found on the same leaf. In fact, it is not improbable 
that the green currant aphis is merely a dimorphic form of the cur-- 
rant aphis. 
THE VARIABLE CURRANT APHIS.’ 
The variable currant aphis is one of the most injurious species. 
The stem-mother is purplish green with white honey tubes. The 
wingless form is dark green, tan, or dark brown, whereas the winged 
1 Amphorophora lactucae ( Kalt.). 2 Myzus dispar Patch. 3 Aphis varians Patch. 
