Comparison of preservation techniques for DNA extraction from hymenopterous insects

Two species of parasitic wasp, Venturia canescens and Leptomastix dactylopii, were killed and preserved by various methods used for Hymenoptera and in mass-collecting devices. Total genomic DNA was subsequently extracted and a 524 bp fragment of the mitochondrial 16S ribosomal RNA gene amplified by PCR. Results for these techniques were compared with that for fresh material and museum specimens. Material from -80 degrees C, 100% ethanol, air-drying in a desiccator, and critical-point dried from alcohol all yielded good results after short and long-term storage, as did specimens from ethylene glycol but not formalin (the latter two being commonly used in pitfall and flight intercept traps). Specimens killed in ethyl acetate vapour and air-dried yielded very degraded DNA which did not successfully PCR. The use of this killing agent is a likely reason for previous reports of inconsistent results obtained from museum specimens, and the now widespread use of critical-point drying of wasps and other insects from alcohol is advocated as a potential source of DNA from rare taxa.