THE MEALY PLUM APHIS. 3 



SYNONYMS. 



1794. Aphis arundinis Fabricius, Ent. Syst., v. 4, p. 212. 



1794. Aphis pruni Fabricius, Ent. Syst., v. 4, p. 213. 



1S86. Aphis phragmiticola Oestlund, List Aphid. Minn., p. 44. 



1911. Hyadaphis vmbcllulariae Davidson, Jour. Econ. Ent., v. 4, p. 559. 



BIOLOGY. 



THE EGG. 



Size 0.55 by 0.27 mm. The newly laid egg is pale green, covered with con- 

 spicuous silvery filaments excreted by the oviparous female. It darkens rapidly 

 and after about 5 days is shining black ; the threads, however, remain silvery. 



LOCATION ON TREES. 



The eggs are laid almost invariably in the axils of lateral buds of 

 year-old or 2-year-old wood. Rarely more than three eggs are to be 

 found to a single bud group. Occasionally eggs are placed in small 

 scars or wrinkles in the bark of twigs. 



HATCHING. 



In 1916 hatching commenced about March 4, and continued for 

 about two weeks. At this time most prune varieties were just starting 

 to leaf, but the Myrobalans were in full leaf; nevertheless hatching 

 was no earlier on the latter trees than on other plums and on apricots. 



THE STEM MOTHER. 



DESCRIPTION. 



Newly hatched. — Pale green; eyes dark red; antennae and legs pale gray; 

 dorsum of head with a median longitudinal narrow pale green stripe ; beak gray. 

 Form oval. 



Antennae one-fourth the length of the body, 5-jointed. Comparative lengths: 

 I, 0.03 mm.; II, 0.035; III, 0.045; IV, 0.05; V, 0.11 (0.060 plus 0.050) ; beak 

 reaching to third abdominal segment, 0.21 mm. in length ; cornicles minute 

 raised pores. Style rounded. Length of body 0.63 mm.; width of body 0.39 

 mm. 



During the first and second instars the color darkens and the dark markings 

 on the head gradually disappear. The characteristic longitudinal stripes of 

 darker green appear during the third and fourth instars. There are 3 of these, 

 1 mediodorsal and 2 dorsolateral. The tarsi, apices of tibiae, cornicles, tip of 

 beak, and distal third of the antennae of the growing nymph become gray. 



After the second molt the nymph assumes an elongate shape, and there 

 appears on the sides and at the abdominal sutures a pruinose " meal." This 

 " meal " is much more scanty and less conspicuous in the stem mother than in 

 later forms. 



Adult. — Yellowish-green with three longitudinal green stripes on dorsum ; 

 eyes dark red ; antennae pale green, distal joint dark gray ; cornicles pale, dusky 

 at apex ; tarsi dark gray ; style pale yellowish green ; apex of beak blackish. 

 Form elongate oval, comparatively flat; newly molted individuals carinate. 





