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Effect of environmental conditions on progeny production by the oriental cockroach Blatta orientalis

Patourel, G.
Entomologia experimentalis et applicata 1995 v.74 no.1 pp. 1-6
Blatta orientalis, cold, cold stress, cold tolerance, egg masses, eggs, embryogenesis, environmental factors, exposure duration, females, fungi, hatching, insects, nymphs, progeny, temperature, viability
Oothecal production by both mated and unmated female oriental cockroaches Blatta orientalis L. (Dictyoptera: Blattidae) was measured at temperatures between 10° and 28 °C. Production was inhibited at 15 °C and below, and only partially recovered when cooled insects were returned to 28 °C. Mean incubation times for oothecae varied from 41.4 to 43.9 days at 28 °C, 60.5 to 60.8 days at 24 °C and 86.8 to 91.7 days at 20 °C depending on RH. No nymphs emerged from oothecae kept continously at 15 °C, 75% RH over a 6 month period, although hatch at both 10° and 15 °C was observed in a few cases when oothecae containing eggs close to hatching (28-35 days from deposition, maintained at 28 °C) were transferred to these lower temperatures. The mean number of nymphs emerging from oothecae (non-hatching oothecae included) increased with temperature over the range 20-28 °C and with RH over the range 43-95% RH. At 28 °C there was a decline in oothecal viability in the range 95-100% RH attributable to fungal attack, and few nymphs emerged from oothecae kept at 0% RH. The viability of oothecae subjected to periods of cold exposure and then returned to 28 °C decreased with decreasing exposure temperature (10° to −5 °C), increasing exposure period (2 h to 30 days) and stage of embryogenesis when exposed (oothecae incubated for 0 to 7 days at 28 °C prior to cold exposure less cold-tolerant than oothecae incubated for 28 to 35 days).