Canadian Forest Service Publications

The combined effect of photoperiod and temperature on the calling behaviour of the true armyworm, Pseudaletia unipuncta. 1987. Delisle, J.; McNeil, J.N. Physiological Entomology 12: 157-164.

Year: 1987

Issued by: Laurentian Forestry Centre

Catalog ID: 14463

Language: English

Availability: PDF (request by e-mail)

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Pseudaletia unipuncta (Haw.) (Lepidoptera: Noctuidae) virgin females, maintained at either 10 or 25°C under LD 12:12 or 16:8 h, started calling at different ages. For a given photoperiod, calling was initiated 11 days later at 10°C than at 25°C, while for a given temperature, calling at LD 12:12 h was 3-4 days later than at LD 16:8 h. At 10°C 50.8% of females did not call within 35 days at LD 12:12 h compared with 30.8% at LD 16:8 h. Calling started earlier in the scotophase at 10°C than at 25°C and at LD 16:8 h than at LD 12:12 h. Under all treatments calling generally advanced on successive nights. The time elapsed between the mean onset time of calling and the mid-scotophase was relatively constant under both photoperiod conditions at 25°C, but at 10°C was more variable. The mean time spent calling increased significantly with calling age but did not differ significantly between the four experimental conditions tested.

Older (15 days) females transferred from 10°C, LD 16:8 h to 25°C at either LD 16:8 or 12:12 h, required less time to initiate calling than younger (5 days) ones. Those transferred from 10°C, LD 12:12 h took the same time, regardless of their age at the time of the transfer. Females experiencing either a decrease or increase in daylength as well as a temperature with individuals that only experienced an increase in temperature.

If temperature was the only parameter changed females that initiated calling soon after the transfer immediately adjusted their calling periodicity to prevailing conditions. When both temperature and photoperiod were altered, it took several days before calling periodicity adjusted to the new regime. The ecological implications of temperature and photoperiodic conditions on the possible autumn migration of P. unipuncta are discussed.