Energy reserves, reproductive status and population biology of overwintering Biprorulus bibax (Hemiptera: Pentatomidae) in southern New South Wales citrus groves.

Information is presented on energy reserves, reproductive status and population biology of over- wintering Biprorulus bibax (Breddin) in southern New South Wales citrus groves. Large numbers of adult bugs overwintered in clusters on orange trees adjacent to a lemon grove at Cudgel in the Murrumbidgee Irrigation Area (M.I.A.). Clusters of up to 50 tightly packed bugs were found on single trees, and dispersed into the adjacent lemons in early October. Clustering was observed on all citrus except lemon. Overwintering bugs were non-reproductive. Individuals obtained from overwintering clusters at Dareton in Sunraysia were larger, heavier and contained greater lipid reserves than bugs which overwintered alone. These differences did not occur in cluster and non-cluster bugs from the M.I.A. Bugs overwintering on lemons in the M.I.A. weighed less and contained lower reserves of lipid than did individuals which overwintered on orange, mandarin and grapefruit. Lipid reserves of B. bibax were not greatly depleted during overwintering. Overwintering in clusters on citrus hosts other than lemon appears to be an important and successful behavioural strategy for B. bibax in commercial citrus groves in southern New South Wales.