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Background: Linear dermatitis is endemic in Iran where most cases occur in the Caspian Sea coast and Fars province. The disease is caused by beetles of the genus Paederus which are active from early spring to beginning of autumn although its incidence rises from May to August. The classic taxonomy of Paederus spp. is based on the male genitalia that is very complex and needs expertise. In this study, we report a DNA-based method to discriminate Paederus fuscipes and Paederus littoralis (=syn: P. lenkoranus , P. ilsae )., Methods: Type specimens were collected from north and south of Iran. Molecular typing of the species was performed using restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction (PCR)-amplified fragments of mtDNA-COI., Results: Sequence analyses of the data obtained in this study showed significant DNA polymorphisms. There were 89 substitutions between COI sequences of the two species. The mtDNA-COI fragment comprises several useful species-specific restriction sites comprising Hae III that could result in distinctively different species-specific PCR-RFLP profiles. The Hae III enzyme cuts the 872 bp PCR amplicon of P. littoralis into 737 and 100 bp and two small nonvisible bands whereas it does not cut P. fuscipes amplicon into fragments., Conclusion: This study demonstrates that molecular typing is useful method and allows one to differentiate between two species and is recommended for discrimination of other Paederus species, which morphologically are indistinguishable or very difficult to be distinguished.

Objective: To evaluate the insecticidal effect of diatomaceous earth (DE) against adults and nymphs of Blattella germanica., Methods: This cross sectional study has been done on the laboratory strain of German cockroaches. Two stages, nymph and adult, were exposed to six dose rates of the DE, 2.5, 5, 10, 15, 20 and 25 g/m(2), at 24, 48 and 72 h exposure period. Mortality (number of dead cockroaches) was assessed after 24 h. Other exposed specimens were transferred to the beakers contained food and water for counting the retard mortality rate after 1 week., Results: Increasing in dose rates of DE increased mortality rate, so that the lowest and highest mortality rates were observed in 2.5 and 25 g/m(2), respectively. The results of the statistical analysis showed no significant difference in the lethality of 50% of DE plus water on the German cockroach nymphs., Conclusions: Due to the resistance of German cockroach against organochloride, organophosphorus, carbamate and pyrethriodes insecticides, it is suggested to use DE for insect's control.