An Investigation of The Behavior And Biology of The Citrus Mussel Scale

Abstract

The citrus industry is subject to a number of serious insect pests. Of these, the most important is a sedentary group known as the ..Armoured Scale Insects (Diaspididae). Ebeling (1950) states bnao they are of greater economic importance to the industry than a ll the other pests put together. A great deal has been published on various aspects o f the biology, ecology and control o f the Diaspididae, much o f the work appearing in the books of Quayle (193S), Ebeling (1950) and Bodenheimer (l9 5 l)» It is very noticeable, however, that the study o f the active larvae, or ’’ crawlers” , of these insects has been re la tiv e ly neglected* This lack of work on crawlers is surprising, since they are the only distributive stage in the l i f e cycle of the species. The adult male is also fre e-livin g during its b rie f l i f e span, but takes no part in the actual distribution o f the species. I t is the position of the female Scale Insect which is important in determining the further spread of the species, since this is the point from which subsequent crawlers w ill start out on their wanderings. The stage in the l i f e cycle responsible for the position of the female is , o f course, the crawler. The crawler is also responsible fo r the p a rallel dis*cribution of the male Scales, so that the female can be fe r tilis e d . The r&le oj. tne adult male is confined to the maintenance of the gene flow* From an economic point of view i t seems desirable that a complete study be made of the biology o f th is distrib u tive stage o f these important pests. Information on factors influencing the hatching (or birth of ovoviviparous species), and emergence from IfiSeath the scale-covering of the female, would be useful. This information might enable forecasts of population increases to be oacie. The expected age composition of the population could also be Ccj-Ci!ate and appropriate control measures instituted* A knowledge o f bhe ej-fects of temperature, rela tive humidity, lig h t intensity, gravity and wind t force on emerged crawlers might open up new p o ssib ilitie s in the control of these insects. Host existing knowledge o f crawlers is lim ited to experiments on those o f the Citrus Red ScaleT Aonidiella aura.ntjj (frfe.sk.), tne Ciorus Mussel Scale, Lepidosaphes beckii (Newm.) and the San Jos6 Scale, Quadraspidiotus perniciosus Comst. The la tte r is a very minor pest of citrus although important in other sections of the fr u it industry# Some details o f the behaviour of crawlers of the San Jos£ Scale are given by Mathys (1953) and Gentile and Summers (1958)* This previous work has been concerned with such matters as the rates of locomotion of crawlers on d ifferen t substrates at various temperatures, the duration of the wandering period, and responses to lig h t, gravity and the smell of citrus.