COMBINED INFLUENCE OF PROTEIN HUNGER AND EGG LOAD ON THE RESOURCE FORAGING BEHAVIOR OF RHAGOLETIS-POMONELLA FLIES (DIPTERA, TEPHRITIDAE)

In patches of five pelted host trees in a large open field, an investi gation was conducted of the combined influence of hunger for protein a nd egg load on responses of marked and released 18-day-old Rhagoletis pomonella (Diptera: Tephritidae) females to proteinaceous food (vials containing bird faeces) and fruit that in terms of the flies' known ov ipositional preferences were high-ranking (hawthorn) or low-ranking (t omato). Consistent with a priori expectation, significantly more femal es denied access to protein up to testing (protein-deprived females wi th low egg load) than females given continuous access to protein (prot ein-fed females with high egg load) were observed on food vials, irres pective of whether tree patches contained hawthorns or tomatoes. As ex pected, significantly fewer protein-deprived than protein-fed females were observed on hawthorns, where they laid significantly fewer eggs. Contrary to expectation, significantly more protein-deprived than prot ein-fed females were observed on tomatoes: where numbers of eggs laid were unfortunately too few to permit accurate assessment of trends. Al so contrary to expectation, significantly more protein-deprived than p rotein-fed females were sighted on foliage and in total in tree patche s, irrespective of whether the patches contained hawthorns or tomatoes . As expected, response patterns of females that had partial access to protein up to testing (intermediate in hunger for protein and interme diate in egg load) were almost always intermediate between the other t wo types of females. Intermediate females appeared to allocate approxi mately equal priority to seeking proteinaceous food to satisfy hunger as to seeking fruit for oviposition. Aided by additional tests conduct ed in field and laboratory cages, we discuss underlying causes of thes e observed response patterns.