Cold hardiness of larvae of the summer fruit tortrix moth, Adoxophyes orana (Fischer von Rosslerstamm) (Lepidoptera: Tortricidae) was examined in the laboratory. Supercooling point of field collected larvae increased significantly from a mean value of -23.9°C in February 1998 to -16.9°C in June 1998. Mean supercooling points for laboratory diapause and non-diapause larvae were -20.7°C and -17.2°C respectively. Short period of acclimation (10 days at 0°C) significantly decreased supercooling point to -24.7°C for laboratory diapause larvae. Acclimation for 12 days at 5°C decreased supercooling point to -19.4°C for non-diapause larvae. Pre-freeze mortality for diapause and non-diapause larvae was also studied. Constant exposure of diapause larvae at -5°C resulted in high mortality (63.1%) after a period of 30 days. in contrast, only 6 days at -5°C were sufficient to cause 100% mortality of non-diapause larvae. Mortality of non-diapause larvae reached 100% after 12 and 18 days at 0 and 5°C respectively. The importance of these findings for the overwintering strategy of A. orana is discussed., Panagiotis G. Milonas, Mathilde Savopoulou-Soultani, and Lit
Larval diapause development and termination and some characteristics of cold hardiness in Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) were studied under field conditions in northern Greece. P. gossypiella overwintering larvae were sampled at 20 to 30 day intervals and subjected to two photoperiodic regimes at 20°C. In larvae kept under a long-day photoperiod (16L : 8D) diapause development was accelerated compared to those kept under a short-day photoperiod (8L : 16D). There was no difference in response to the two photoperiods after February. Mean number of days to pupation of P. gossypiella overwintering larvae decreased progressively through the sampling period, from November to April. Chilling is not a prerequisite but does accelerate diapause development. Supercooling points for P. gossypiella overwintering larvae ranged from -14 to -17°C with the majority dying after freezing.
Functional responses of immature stages of Propylea quatuordecimpunctata (L.) to varying densities of Aphis fabae Scopoli
reared on Vicia faba L. were evaluated under laboratory conditions. All larval stages of the predator were starved for 12 h prior
to being placed individually for 24 h in plastic containers with different densities of its prey, A. fabae, on potted V. faba plants.
Logistic regression analysis of the proportion of aphids consumed as a function of initial density indicated that all larval instars of P.
quatuordecimpunctata exhibited a type II functional response when searching for A. fabae on V. faba plants. Attack rates (0.059,
0.057, 0.065 and 0.064) and handling times (6.18, 2.37, 1.06 and 0.44) for first to fourth instar larvae, respectively, were estimated
using Holling’s disc equation.
The fecundity of the pseudococcid predators Nephus includens (Boheman) and N. bisignatus (Kirsch) (Coleoptera: Coccinellidae), fed on Planococcus citri Risso (Hemiptera: Pseudococcidae), was studied at several constant temperatures (15, 20, 25, 30, 32.5 and 35°C). With additional data for the development of the immature stages, life-fecundity tables were constructed and some population parameters calculated. The average total fecundities of N. includens at the above temperatures were 49.2, 97.8, 162.8, 108.5, 87.4 and 31.1 eggs/female, and average longevities 99.5, 84.7, 69.5, 61.1, 49.6 and 30.1 days, respectively. The net reproductive rates (Ro) were 8.0, 32.2, 60.7, 32.6, 20.7 and 2.6 females/female, and the intrinsic rates of increase (rm) 0.014, 0.041, 0.083, 0.086, 0.077 and 0.024 females/female/day, respectively. The average total fecundities of N. bisignatus at 15, 20, 25, 30 and 32.5 ¿C were 54.7, 72.1, 96.9, 56.0 and 22.8 eggs/female, and average longevities 116.1, 108.7, 71.8, 68.8 and 43.7 days, respectively. The net reproductive rates (Ro) were 13.9, 26.4, 31.3, 15.2 and 3.6 females/female and the intrinsic rates of increase (rm) were 0.017, 0.035, 0.060, 0.051 and 0.024 females/female/day, respectively. The survival of females at each temperature was fitted using a Weibull distribution [S(t) = exp(-(t/b)c)]. Furthermore two mathematical models [Enkegaard equation: F = (a+b+x).e(c+d.x), Analytis equation: F = a.(x-xmin)n .(xmin- x)m] were fitted to the fecundity data.