Movement and distribution of adult Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) in stored wheat in response to temperature gradients, dockage, and moisture differences

2005 ◽  
Vol 41 (4) ◽  
pp. 401-422 ◽  
Author(s):  
Fuji Jian ◽  
Digvir S. Jayas ◽  
Noel D.G. White
2005 ◽  
Vol 137 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Fuji Jian ◽  
Digvir S. Jayas ◽  
Noel D.G. White

AbstractAdult Cryptolestes ferrugineus (Stephens) were reared at 30 °C or acclimated to 15, 25, or 35 °C for different periods (2 days or 1, 2, or 5 weeks). Populations 1 day old, 1, 5, 10, or 20 weeks old, or of mixed age were held in 10 cm × 10 cm × 100 cm wheat columns (14.5% ± 0.2% moisture content) with a temperature gradient (10 °C/m, 25–35 °C) or a constant temperature (25 or 30 °C) for 1, 6, or 12 days; movement and distribution were then determined. Acclimation to 25 °C for a short time (less than 2 days) did not influence adults' response to temperature in the wheat column. Adults acclimated to 15 and 35 °C responded differently to temperature in the wheat column, preferring temperatures above 30 and 35 °C, respectively. Increasing the duration of the acclimation to 15 or 35 °C resulted in higher aggregation. Acclimation temperature might be more important than exposure time for influencing insect behaviour. During their movement in the wheat columns, adults were also acclimated to the tested temperatures, and they did not always stay in a warmer area if the "cold" area was warmer than 25 °C. Adults that were 1 day old had a lower response (i.e., less movement) to temperature gradients than the older insects. Among the older insects, the response to temperature gradients did not decrease with increasing age, even at 20 weeks.


1980 ◽  
Vol 58 (9) ◽  
pp. 1524-1534 ◽  
Author(s):  
N. D. G. White ◽  
R. N. Sinha

The consequences of infestation of bulk-stored wheat by multiple species of insects were determined for 60 weeks at 30 ± 2 °C. Eight 204-L drums containing wheat at 15.5% moisture content were used as three distinct systems: (I) Control system (two drums), insect free; (II) RST system (three drums), infested with the grouping of Rhyzopertha dominica F., Sitophilus oryzae (L.), and Tribolium castaneum (Herbst); and (III) COT system (three drums), infested with the grouping of Cryptolestes ferrugineus (Stephens), Oryzaephilus surinamensis (L.), and T. castaneum. At triweekly intervals carbon dioxide, oxygen, temperature, grain moisture, seed damage, grain weight, dust weight, fat acidity values (FAV), seed germination, microflora, and the numbers of insects and the mite Tarsonemus granarius Lindquist were measured. Seeds died by week 15 and bacterial infection on them increased in all systems. The seed FAVs in the RST system peaked by week 30 and then declined steadily while these values were increasing continuously in the Control and levelling off in the COT systems. Insects multiplied exponentially for 6–15 weeks and then declined sharply or maintained oscillating populations; Sitophilus and Oryzaephilus were unable to survive in the presence of the other insects.


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