PCR-based gut content analysis of insect predators: using ribosomal ITS-1 fragments from prey to estimate predation frequency

We used polymerase chain reaction to determine whether Ostrinia nubilalis ( Hubner) (Lepidoptera: Crambidae) DNA was present in the guts of larvae and adult males and females of the generalist predator Coleomegilla maculata De Geer (Coleoptera: Coccinellidae). The predators were fed Ostrinia nubilali s egg masses and allowed to digest at either 20 degreesC or 27 degreesC for time spans ranging from 0 to 12 h. Four primer pairs, specific for 0. nubi lalis were developed, using a nuclear ribosomal RNA sequence including part of the 18S gene, the complete internal transcribed spacer (ITS-1) region a nd part of the 5.8S gene. These primers amplified four sequences that were 492,369,256 and 150 base pairs long. We found a significant negative effect of time since feeding on the number of bands that could be detected. The s hortest fragment was detected for the longest time after feeding (up to 12 h). We found no effect of predator weight, sex, developmental stage, or mea l size on the time course over which bands of varying lengths could be dete cted.