THE MEALY PLUM APHIS. 15 



posited near the growing stem mothers on plums. Throughout April 

 lampyrid beetles (Podahrus comes Le Conte, P. binotatus Le Conte 

 var., and Telephones divisus Le Conte) appeared locally. During 

 May syrphus-nY larvae (especially Catabomba pyrastrl Linnaeus) and 

 lad} T bird adults and larvae (especially Hippodamia convergens 

 Guerin) abounded, as did also a few hemerobiid larvae. Nevertheless 

 these predators made little apparent headway in reducing infes- 

 tations. 



Observations made in June, 1915, indicated that Hippodamia con- 

 vergens was by far the most beneficial of the ladybirds. 



The Typha colonies were preyed on by the larvae of Syrphus ; those 

 on Phragmites by beetles of the Hippodamia group and by Leucopis 

 larvae; 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 itself 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 

 of 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 rarety 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. 



