DISTRIBUTION AND BEHAVIOR OF STERILE MEDITERRANEAN FRUIT-FLIES IN A HOST TREE

Sterile Mediterranean Fruit flies were released into orange trees near Tapachula, Mexico and studied from observation platforms in order to quantify post release behaviour. Fly numbers decreased precipitously during the two days following a release. Periods of rain did not depress numbers. More released flies were found in the tops of trees in early morning and late afternoon. There was a preference for upper E and S quadrants to be favoured early in the morning and upper N and W quadrants in the late afternoon. Flies moved lower in the tree and became more aggregated when temperatures rose above 30-degrees-C. Males form aggregations which have a mean nearest neighbour distance of about 10 cm. Sexual activity predominates in the morning. After adjusting for surface area differences, about 25 times more flies were found on ripe fruit than leaves. On leaves, females tended to choose upper surfaces and males the lower surface. The results are discussed in relation to the needs of an operational sterile release programme.