Some aspects of the biology of Coccus hesperidum L., with particular reference to the feeding behaviour

Abstract

Past work on the morphology and biology of C. hesperidum is reviewed. Examination of the feeding sites, by means of sections and whole mounts, showed that penetration by the stylets is due to mechanical pressure, the stylets taking an intracellular path to the phloem with no visible effects on the cell contents. A stylet sheath surrounds the stylets and remains in position following their retraction. The origin of this sheath is discussed and attributed to the saliva. A tactile stimulus is suggested as the initial stimulus directing the stylets to the phloem. A study of stylet retraction indicated that retraction is aided by the labium and the presence of part of the stylets within the crumena. The time taken for retraction varied from 6 to 70 minutes, whilst the speed increased during retraction. Separation of the stylets revealed an intrinsic tension in the mandibles which causes them to coil up. This tension is indicated as being overcome by the surface tension of the saliva existing between the maxillae and mandibles. This is suggested as a basic function of the saliva, responsible for the presence of the stylet sheath. Growth continues throughout each respective instar although increase in the length of the stylets during the life-cycle is small. A method of studying the feeding behaviour on the leaves, throughout the insect's life-cycle, is described. Most individuals remain in the same position throughout the lifecycle, a single penetration by the stylets lasting for the duration of each respective instar. At ecdysis, the shedding of the old stylets appears to aid the initial extension of the new stylets. Observations were made throughout the life-cycle which lasted for 69 days at 27°C. Activity was restricted mainly to the first few hours although the ability to move is retained until parturition.