The Humped-back theory of plant species richness, a theory related to Grime's C-S-R 'triangular' model, has been widely discussed, and some evidence has been claimed in support of it. The theory suggests that species richness is maximal at intermediate levels of productivity, i.e., at intermediate positions on a stress/favourability gradient. We sought evidence for the theory from 90 stands of native podocarp/broadleaved and beech forest in the Coastal Otago region, with an adjustment made for the effect of stand area on species richness.
Honeydew, the sugary exudate of the scale insect Ultracoelostoma brittini, is an important food source in black beech (Nothofagus solandri var. solandri) forests in the South Island of New Zealand. Two of the most prominent foragers of honeydew are honey bees (Apis mellifera) and wasps (Vespula germanica and V. vulgaris). Observations in the field and using a captive bee hive were used to investigate competition between bees and wasps feeding on honeydew.
The standing crop and daily production of honeydew by Ultracoelostoma brittini on Nothofagus solandri: var solandri was measured on 28-29 August 1990 near Oxford, Canterbury. In 64 quadrats of 125 cm², all 740 active individual insects were mapped by their anal threads and honeydew production was recorded every three hours over 24 hours. Mean production of honeydew per insect over 24 hours was 0. 1 69 mul, but ranged from zero (4% of all active insects) to 11.5 mul. Standing crop Peaked just after dawn, and production was apparently higher at night.