A SIMPLE GRAPHICAL TECHNIQUE FOR DISPLAYING INDIVIDUAL FERTILITY DATAAND COHORT SURVIVAL - CASE-STUDY OF 1000 MEDITERRANEAN FRUIT-FLY FEMALES

1. A graphic technique is presented in which data on age-specific repr oduction of individuals are portrayed using: (i) a horizontal life lin e, the length of which is proportional to individual longevity; (ii) c olour-coded segments depicting the level of reproduction at each age; and (iii) a cohort survival schedule created by rank-ordering individu al life lines from shortest- to longest-lived. 2. The resulting graphi c, referred to as an event history diagram, portrays data at the indiv idual level and thus allows visual comparisons of detailed life-histor y patterns such as age of first reproduction, longevity, ages of high, medium, low and zero reproduction, and post-reproductive period, 3. E xample graphs are shown for reproductive and longevity data gathered o n 1000 medfly females. The average female lived 35.6 days and laid 759 .3 eggs and therefore the graphs display information for 35 600 fly da ys and the age-distribution of laying for 759 300 eggs. 4. Because the graphics provide a means for visualizing large amounts of data precis ely and efficiently, they reveal details and nuances in the data that are not apparent from conventional graphic methods. 5. The advantages of longitudinal data gathered on individuals and reasons why visualizi ng individual-level data is important are discussed.