Full-text - Norsk entomologisk forening

404 Torgeir Edlnnd19630 1964.&000 0eouW0 5wlWuOr00 I-4z .uWa.wld z1-03 0 5 10 15 20 25 3 0 5IAPRIL196 3 5 10 15 20 25 301966 5 10 15 20 2 5 30DAYS AFTER THE FIRST TRAPPINGIMAYFig. 6. Relationship between number of spermatophores and date oftrapping for 38 females trapped in 1963 and for 34 females trapped in1964. (Regression equations: 1963, y = 0.1447~ + 0.7003, r = 0.574***;1964, y = 0.2897~ - 2.7299, r = 0.632***). *** statistically significantat the 1% level.In gcneral there is no relation between the fecundity of animalsand their abundance in nature (Andrewartha and Birch1954). However, in species which are severe pests in certainyears, but relatively scarce in others, high fecundty whichallows the species to increase rapidly during favourable years,is an important factor in explaining their sporadic outbreaks.The probable strong fluctuations of E. transversa could thus bedue to the observed high reproductive capacity and to variousmortality factors, of which virus diseases may be one (Edland1965).E. transversa is a pest of such severity that it would deservefurther studies, particularly from the point of view of controlmeasures, for which widely different approaches should be considered.