USING CROWDING AND SPACING FOR RAISING THE

ERI SILKWORM PHILOSAMIA RICINI HUTT

[70]

Eid¹, M.A.A. and M.N. El-Basiony²

ABSTRACT

          The effect of spacing was studied by rearing Philosamia ricini larvae in separation and in crowding throughout the larval stage. The other treatments were separating larvae after passing the four sucessive instar larvae under crowding. During the last (fifth) instar, the general pattern of behaviour was examined. The crowds were generally more active than all conditions of separation. The highest activity devoted to feeding applied to those separated in the fifth instar. The crowds were active apart from feeding more than about three times as much as were the conditions of separation.           It has been claimed that larvae which were separated from crowded condition in the fifth instar gave rise to the least mean total duration and highest rate of growth. The least average fresh weight of mature larvae was induced by crowded condition. The mature larval and coccon weights concerning conditions of separation were gradually increased with the increase of instars passed under crowding. The mortality of crowded larvae was lower in the first, three sucessive instars than separated conditions. In the remainder instars, the mortality of those separated from fourth and fifth instars was lower than all conditions.