4 BTJLLETIX 771, IT. S. DEPARTMENT OP AGRICULTURE. 



Antennae on very short frontal tubercles, barely one-third the length of the 

 body, 5-jointed. Comparative lengths : I, 0.075 mm. ; II, 0.06 ; III, 0.30 ; IV, 

 0.14; V, 0.22 (0.08 plus 0.14). Beak, length 0.26 mm., reaching to second coxre; 

 cornicles, 0.045 mm. ; style, 0.17 mm. Cornicles wartlike, style ensif orm. Pro- 

 thorax and all abdominal segments bearing small, pale, lateral tubercles. Body 

 bearing a sparse, inconspicuous clothing of granular " meal,'' most abundant at 

 the sutures. Length of body (style included), 2.39 mm. ; width of body, 1.06 mm. 



HABITS AXD LENGTH OF XYMPHAL LIFE. 



* 



After hatching, the young aphicls seek out buds, often massing on 

 those most advanced, and contrive to penetrate to the inner portions. 

 On unopened buds they feed on the tender apical portions and num- 

 bers of them die in such situations. Newly-hatched aphids move 

 awkwardly on rough spiny leaf surfaces and frequently fail to make 

 headway. This was observed especially in connection with Myroba- 

 lan plum leaves, and perhaps explains the fact that the stem mothers 

 on this tree have a high percentage of mortality in theirearly stages. 



After the blossoms shoot out the aphids feed on the petioles or on 

 the outside of the sepals. In the leaf bud they feed generally on the 

 under (outer) surface of the unfolding foliage and less abundantly 

 on the reverse side. A favored point is that at the junction of sepal 

 and petiole on the flower stalks. 



The first stem mothers matured on the plums at time of full bloom 

 (March 19, in 1916), their growth being the more rapid on forward 

 trees. On March 25 it was estimated that on the most advanced trees 

 85 per cent of the aphids were mature, while on the most backward 

 only 20 per cent were full grown. At this time the mature stem 

 mothers were on the underside of the leaves ; none were remaining on 

 the fruit stalks. On March 28 virtually all stem mothers on forward 

 trees were mature ; on most backward trees 50 per cent were still im- 

 mature. By April 5 no more immature stem mothers were found. 



Five stem mothers raised on potted Myrobaian seedlings developed 

 in from 13 to 17 days. This time is perhaps less than in the average 

 orchard, since the quality of food available for the newly-hatched 

 aphid is often poor, while the seedlings were well in leaf at the time 

 the experimental eggs hatched. It should be stated that the tempera- 

 ture in 1916 during the first part of the development of the stem 

 mother was higher than usual for that time of year. 



REPRODUCTION. 



The stem mothers deposit on an average about 4 young a day 

 during a period of from 3 to 5 weeks. The rate of fecundity rises 

 rapidly at first, maintains an even zenith for some three weeks, and 

 then rapidly declines. Stem mothers may live for as long as three 

 weeks after they have deposited their complement of young. 



