The relative acceptabilities of three Australian Menispermaceae as food plants for larvae of the fruitpiercing moth, Othreis fullonia

Abstract

AbstractThe acceptability of three widely distributed Australian Menispermaceae, Tinospora smilacina Benth., Sarcopetalum harveyanum F. Muell. and Stephania japonica (Thunb.) Miers, as food for larvae of the fruitpiercing moth, Othreis fullonia (Clerck), was examined in three laboratory experiments. When larvae were presented with plant species individually total development times were shortest on T. smilacina and longest on S. japonica, despite relatively similar consumption rates within most instars. T. smilacina elicited greater (P<0.05) relative growth rates than S. japonica in all instars except the 6th. In the second experiment, when larvae were allowed to select from each of the 3 plants, no S. japonica was chosen by 1st instars and it represented only 3.7% of food consumed by 2nd instars. Significantly more T. smilacina was eaten in each instar than S. japonica, and more than S. harveyanum except in the 2nd and 4th instars. The final experiment examined the abilities of larvae to switch hosts when forced after the 1st and 3rd instars. After the first or second food change largest average headcapsule widths were associated with feeding on T. smilacina as the most recent food. Feeding by final instars on T. smilacina also resulted in the shortest development time and highest puparial weights. While some larvae survived irrespective of plant sequence 83.3% of the recorded mortality occurred while larvae were exposed to S. japonica, principally during the 1st instar. These experiments lend support to field observations which suggest that T. smilacina is a major host of O. fullonia while S. japonica is not. S. harveyanum is probably an important alternate host when T. smilacina is scarce.