Development and Morphometrics of the Turkestan Cockroach (Periplaneta lateralis) Under Solitary and Cohort Rearing at...

The Turkestan cockroach, Periplaneta lateralis (Walker), is an invasive peridomestic pest expanding across southwestern U.S. habitats, where it has been reported to replace the Oriental cockroach, Blatta orientalis L. Life-history advantages may contribute to this expansion, but its developmental parameters remain poorly characterized. We measured development at 25 and 30 °C under solitary rearing, solitary rearing with photographic monitoring, and cohort rearing. Developmental time was significantly shorter under cohort than solitary rearing. Solitary-reared males and females required 219.8 ± 1.45 and 225.0 ± 2.07 d at 25 °C and 181.5 ± 2.51 and 190.2 ± 2.13 d at 30 °C, respectively. Cohort-reared males and females required 120.2 ± 7.43 and 112.4 ± 9.20 d at 25 °C and 76.5 ± 2.66 and 77.6 ± 1.30 d at 30 °C. Across the two solitary-rearing experiments, individuals completed 7-11 instars. Morphometric measurements increased across instars but overlapped among late instars, making it an unreliable trait to use to determine instar. Degree-day accumulation was consistent across temperatures under cohort rearing but not under solitary rearing. Because the rearing protocols differed in housing, handling, monitoring, and incubator conditions, the difference cannot be attributed solely to social contact. These results demonstrate that laboratory rearing conditions should be considered when extrapolating laboratory estimates to field populations and when comparing laboratory strains with field strains.