Is repeated cypermethrin fumigation dangerous for the mitochondrial DNA in dry insect samples?

Entomological collections are the target of various insect pests, e.g. carpet beetles (Dermestidae) and booklice (Psocoptera) which can damage and completely destroy dry specimens in a relatively short time. Collections in the National Museum, Czech Republic (NMP) including the entomological ones are protected by fumigation using commercially available smoke shells ‘Cytrol Super SG’; fumigation is performed twice a year. The active insecticidal substance of these smoke shells is cypermethrin (6.25%). We tested whether the repeated cypermethrin fumigation of the NMP entomological collections negatively affects the quality of mitochondrial DNA in dry specimens and prevents the subsequent use of these samples for molecular analyses required for identification, taxonomy, systematics, and phylogenetic studies. We used 32 freshly fixed specimens of the flower chafer Oxythyrea funesta (Poda von Neuhaus, 1761) and 32 freshly fixed specimens of the brown-tailed cockroach Supella longipalpa (Fabricius, 1798). One half of specimens of both species was stored outside NMP and not fumigated (negative control), and the other half was deposited in collection hall with the NMP insect collection and directly exposed to the fumigation. Subsequently, all specimens were processed in a molecular laboratory under a standardized protocol using one leg as the source tissue after each fumigation, and the 658 bp long barcoding region of the cytochrome oxidase I (cox1) as the testing gene fragment. Results of the PCR product electrophoresis and the sequences acquired confirmed that the repeated fumigation had no negative effect on tested samples.