THE MEALY PLUM APHIS. 15 
posited near the growing stem mothers on plums, Throughout April 
lampyrid beetles (Podabrus comes Le Conte, P. binotatus Le Conte 
var., and Zelephorus divisus Le Conte) appeared locally. During 
May syrphus-fiy larvee (especially Catabomba pyrastri Linneeus) and 
ladybird adults and larve (especially Hippodamia convergens 
Guérin) abounded, as did also a few hemerobiid larve. Nevertheless 
these predators made little apparent headway in reducing infes- 
tations. 
Observations made in June, 1915, indicated that Hiypodamia con- 
vergens was by far the most beneficial of the ladybirds. 
The Typha colonies were preyed on by the larve of Syrphus; those 
on Phragmites by beetles of the Hippodamia group and by Leucopis 
larve: and late in the fall the sexual females were attacked by syr- 
phids and Triphleps. 
Internal parasitism in the writer’s opinion is of very rare occur- 
rence. Occasionally he has observed parasitized specimens in nature. 
CONTROL SUGGESTIONS. 
There are two especially vulnerable periods in the annual life cycle 
of the mealy plum aphis—one in early spring when the stem mothers 
are growing and the other in late fall when the sexual females are 
developing on the winter hosts. Unfortunately at these two periods 
the enemies of the aphis are very scarce, but the aphis itse!f is more 
easily destroyed than at other times by artificial substances. Both the 
stem mothers and the oviparous females have a scant protective cover- 
ing of “ meal” and both live for the most part on exposed surfaces of 
the plant, whereas the aphids of the spring and summer generations 
bear a comparatively thick coating of meal and live in great part in 
curled foliage. Contact insecticides, which have little effect on aphids 
ot the intermediate generations, easily destroy the stem mothers and 
the egg-laying females. 
SUMMARY. 
The mealy plum aphis in California is a decided pest of plums, 
prunes, and, to a lesser degree, apricots. Besides devitalizing the 
trees it causes small-sized fruits and early drops, and is probably con- 
cerned in a measure with apical cracking of prunes. 
In 1916 winter eggs hatched between March 4 and 18 and early 
stem mothers began reproduction about March 20. It appeared 
that normally from 3 to 5 generations were raised on the winter 
hosts, but rarely series of wingless generations persisted until the fall. 
The aphids of the earlier generations were mostly wingless like the 
stem mothers, and the individuals of the later generations mostly 
winged, and after the middle of June virtually all the insects pro- 
duced developed wings. 
