14 BULLETIN 74, U. S. DEPARTMENT OF AGRICULTURE. 
Myrobalan seedlings.. Within the period October 20-November 23,40 
oviparous females matured in an average of 19.1 days, the period 
of development ranging from 16 to 22 days. On Myrobalan plum 
the development was slightly slower than on Agen (french) prunes. 
HABITS AND OVIPOSITION. 
The females feed normally on the under surface of the leaves, but 
occasionally also on tender stalks, especially of sucker growth. The 
males frequently arrive before the females are mature and settle 
down beside the immature aphids. Copulation takes place very 
soon after the female casts her fourth skin, and a male may copulate 
with more than one female. As the males are much less abundant 
than the females this practice is probably common and was often 
noticed in the cages. Toward the middle of November, 1916, large 
numbers of immature females were blown off the trees by winds and 
perished. In some orchards this only thinned out the infestation to 
a small degree, as plenty of mature females had been observed previ- 
ous to the coming of the high winds, but in others wherein the sexes 
were not so advanced it destroyed the majority of the aphids. The 
oviparous females bear only a scant coat of “meal” and may be 
easily confused in the orchard with those of Phorodon humuli 
Schrank and Aphis cardui Linneus, both of which are contempo- 
raneous with arwndinis. They are less likely to be confused with the 
plump reddish-brown oviparous form of Rhopalosiphum nympheae 
Linneeus, : 
As a rule the female commences oviposition within 24 hours of 
copulation, but this was delayed in some cases as long as 5, and in 
one instance 10 days. In cages never more than 2 eggs, and more 
often only 1, were laid in one day by a single aphid. 
Sixteen females laid an average of 4.1 eggs in the period Novem- 
ber 9—-December 18. In the early part of this period the average was 
6, while toward the end it was 3.5. Not over 7 eggs were deposited 
by one female. There was a marked tendency to deposit the eggs 
over a long period—as much as three weeks—and the females after 
depositing an egg or eggs on the stems generally returned to the leaf, 
remaining there until the time for the deposition of the next egg. 
The females usually died within a week of depositing their last egg, 
but in some cases lived longer, and one aphid lived beyond three 
weeks. It appeared, however, that those that persisted had not rid 
themselves of all their ova, as they did not have the shrunken ap- 
pearance of sterile aphids. 
NATURAL ENEMIES. 
The mealy plum aphis, both on winter and summer hosts, is preyed 
upon by a large series of natural enemies. As early as March 17, 
1916, a few eggs of Syrphidae and Chrysopidae were observed de- 
