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Pterochhroides (PferocJilorus, Laclmus) persicae, Choi., of which 

 Dryobius amygdali, Goot, is a synonym according to Mordwilko, 

 occurs in Transcaucasia and Turkestan and has also been reported 

 from Palestine. In addition to peaches (Prunus jjersica), it occurs on 

 almonds {Amygdalvs commimis), sloes {Primus divaric.a(a), plums 

 {Prunus domestica), apricots {Primus armeniaca), quinces {Cydonia 

 vulf/aris) and apples (Pyrus mains). Though it can breed and complete 

 its cycle on peaches, apricots and sloes, on the other plants the colonies 

 die out after a short time. The examples bred on peaches are the 

 largest, those on almonds being the smallest, and those on apricots and 

 plums of an intermediate size. 



P. persicoe, Choi, Avinters in the egg-stage, the young appearing 

 early in spring at the end of February or in March according to the 

 conditions. The stem-mothers are very sluggish ; they live for 5'J 

 days or more and give birth to living larvae, the exact number 

 of which has not been determined. The wingless parthenogenetic 

 females of the next generations resemble the stem-mother, but are of 

 larger size. The number of generations obtained in the laboratory was 

 eleven, but it is thought that more occur in nature. The larvae moult 

 four times, maturing and becoming viviparous a few days after the 

 last moult. Tables are given showing the intervals between the moult 

 of the first and second generations and the duration of the larval 

 period for each generation ; the last table shows that the fifth, sixth 

 and seventh generation develop in the shortest time, while the ninth 

 and tenth take the longest : the larval stage is thus shorter in summer 

 and longer in spring and autumn. Other tables deal with the number 

 of larvae born of the wingless parthenogenetic females ; this number 

 declines with the age of the mother, being highest in the first half of 

 its life, and with the generations to which the mother belongs ; the 

 average figure for the second, third and sixth generations is three 

 larvae per day, for the fourth and eighth, two larvae, and for the seventh 

 and ninth, one larva per da}'. According to Plotnikov winged 

 parthenogenetic females appear in July, but the author has observed 

 them much earlier, from the middle of May till autumn, their 

 maximum being in July and August. In the year in question, no sexual 

 forms were observed, the hibernating eggs having been laid by the 

 Avingless parthenogenetic females ; further observations are required 

 to show whether P. persicae normally differs in this respect from allied 

 species of Aphids, which usually produce sexual forms in autumn that 

 give rise to the hibernating eggs. Another peculiarity observed in 

 P. persicae consists in the ability of the same individual first to 

 give birth to larvae and then to deposit eggs. The oviparous forms 

 j3ractically differ in no way from the wingless females, except for their 

 larger size. The individuals of the last few autumn generations lay 

 eggSj generally in heaps of five or six on the lower sides of the branches. 



The colonies of P. persicae are usually found on the under-side of 

 stout or medium-sized branches, although they sometimes occur on 

 the smaller ones and in rare cases at the base of the trunk near the 

 ground. Migrations, in which whole colonies frequently participate, 

 occur owing to shortage of food, the movement of the sap in the tree, 

 the attacks of parasites and other enemies, and also from the effect 

 of light, shaded spots being preferred. By means of these movements 

 the Aphids frequently reach other trees, either by way of adjoining 



