Development of the Arboreal Stages of the Pine False Webworm (Hymenoptera: Pamphiliidae)

Abstract

The relationships between temperature and rates of development of eggs and larvae for the pine false webworm, Acantholyda erythrocephala (L.), were determined at constant temperatures in the laboratory. Observed mean development times of eggs ranged from 35.8 d at 10.7°C to 8.2 d at 26.7°C. Some egg development took place at temperatures between 3.9 and 7.0°C, but the eggs failed to hatch. Interpolation techniques were used to predict development times at these low temperatures. Mean developmental times for larvae ranged from 75.5 d for females at 7.3°C to 13.9 d for males at 29.0°C. Average development times of females were greater than those of males at all temperatures. Models incorporating the relationships between temperature and development rates of eggs and larvae were constructed to simulate the development of these arboreal stages under field conditions. Model predictions were compared with field observations of egg hatch and larval drop using temperatures recorded in meteorological shelters, plantation canopies, and larval webs as model inputs. Air temperatures recorded in a plantation canopy provided the best prediction of egg hatch, which suggests that egg development was not greatly affected by direct solar radiation. Average temperatures within larval webs were as much as 2.4°C warmer than ambient air temperatures. Using air temperatures as model inputs resulted in deviations of <3 d between observed and predicted times of larval drop from the branches to the ground. The use of canopy temperatures as inputs slowed predicted development and increased the deviations between observed and predicted larval drop. Using web–temperature corrections for models of developing larvae reduced these deviations, but did not provide as accurate predictions as air temperature alone.