Studies on the cold-hardiness and overwintering of Spodoptera litura F. (Lepidoptera: Noctuidae). II. The lower lethal temperature.

ABSTRACTGypsy moth Lymantria dispar (GM) is a polyphagous insect and one of the most significant pests in the forests of Eurasia and North America. Accurate information on GM cold hardiness is needed to improve methods for the prediction of population outbreaks, as well as for forecasting possible GM range displacements due to climate change.As a result of laboratory and field studies, we found that the lower lethal temperature (at which all L. dispar asiatica eggs die) range from –29.0 °C to –29.9 °C for three studied populations, and no egg survived cooling to –29.9 °C. These limits agree to within one degree with the previously established cold hardiness limits of the European subspecies L. dispar dispar, which is also found in North America. This coincidence indicates that the lower lethal temperature of L. dispar is conservative.Thus, we found that the Siberian populations of GM inhabit an area where winter temperatures go beyond the limits of egg physiological tolerance, because temperature often fall below –30 °C. Apparently, it is due to the flexibility of ovipositional behavior that L. dispar asiatica survives in Siberia: the lack of physiological tolerance of eggs is compensated by choosing warm biotopes for oviposition. One of the most important factors contributing to the survival of GM eggs in Siberia is the stability of snow cover.SummaryWithin the geographical range of Siberian gypsy moth populations, extreme temperatures go beyond the limits of the physiological tolerance of wintering eggs (–29.9 °C), and their survival depends on the choice of warm biotopes for oviposition.

Download Full-text

Behaviour and cold hardiness of the purple stem borer in winter, colonizing more northerly latitudes

10.1101/819417 ◽

2019 ◽

Author(s):

Jianrong Huang ◽

Guoping Li ◽

Haixia Lei ◽

Chunbin Fan ◽

Caihong Tian ◽

...

Keyword(s):

Cold Hardiness ◽

Species Distribution Model ◽

Stem Borer ◽

Distribution Model ◽

Late Winter ◽

Suitable Habitat ◽

Temperature Threshold ◽

Lethal Temperature ◽

Breeding Area ◽

Lower Lethal Temperature

AbstractTo escape or alleviate low temperatures in winter, insects have evolved many behavioral and physiological strategies. The rice pest insect, the purple stem borer, Sesamia inferens (Walker) is currently reported to be expanding their northern distributions and causing damage to summer maize in Xinxiang, China. However, their method of coping with the lower temperature in the new northern breeding area in winter is largely unknown. This paper investigates the overwinter site of S. inferens, and identifies the cold hardiness of larvae collected from a new breeding area in winter and explores a potential distribution based on low temperature threshold and on species distribution model, MaxEnt. The results show that the overwintering location of the S. inferens population is more likely to be underground with increasing latitude and,in the north, with the temperature decreasing, the larvae gradually moved down the corn stalk and drilled completely underground by February 18th. Those who were still above ground were all winterkilled. The cold hardiness test shows the species is a moderate freeze-tolerant one, and Supercooling Points (SCP), Freezing Points (FP) and mortality rate during the middle of winter (January, SCP: −7.653, FP: −6.596) were significantly lower than early winter (October) or late winter (March). Distribution in the new expansion area was predicted and the survival probability area was below N 35° for the Air Lower Lethal Temperature (ALLT50) and below N 40° for the Underground Lower Lethal Temperature (ULLT50), The suitable habitat areas for S. inferens with MaxEnt were also below N 40°. This study suggests the overwinter strategies have led to the colonization of up to a five degree more northerly overwintering latitude. This behavior of S. inferens could help maize producers to propose a control method to increase pest mortality by extracting the maize stubble after harvest.

Download Full-text

POSSIBLE DUAL COLD-HARDINESS STRATEGIES IN CISSEPS FULVICOLLIS (LEPIDOPTERA: ARCTIIDAE)

The Canadian Entomologist ◽

10.4039/ent1181309-12 ◽

1986 ◽

Vol 118 (12) ◽

pp. 1309-1311 ◽

Cited By ~ 23

Author(s):

Paul G. Fields ◽

Jeremy N. McNeil

Keyword(s):

Cold Hardiness ◽

Prolonged Exposure ◽

Extracellular Fluid ◽

Ice Crystals ◽

The Other ◽

Ice Formation ◽

Lethal Temperature ◽

Other Hand ◽

Freeze Tolerant ◽

Lower Lethal Temperature

Insects are usually classified as either freeze-intolerant or freeze-tolerant (Danks 1978; Sømme 1982; Baust and Rojas 1985). Freeze-intolerant species cannot survive the formation of ice in their bodies and typically lower their supercooling points (SCP), the temperature of spontaneous ice formation, during the winter months (Sømme 1982). This is the lower lethal temperature for the insect, although prolonged exposure to temperatures above this may be harmful (Turnock et al. 1983). On the other hand, freeze-tolerant insects can survive the presence of ice crystals in their extracellular fluid and usually have nucleators that prevent supercooling below – 10°C (Zachariassen 1982).

Download Full-text