Research paperThe complete mitogenomes of Calameuta filiformis (Eversmann, 1847) and Calameuta idolon (Rossi, 1794) (Hymenoptera: Cephidae): The remarkable features of the elongated AÂ +Â T rich region in Cephini

- The complete mitogenomes of stem borers, Calameuta filiformis and Cl. idolon, are sequenced and characterised.
- A rearrangement in IQM gene cluster and a length expansion in rrnS gene are suggested as synapomorphies for Cephini.
- A remarkable length increase is also observed in their A + T rich region.
- Characterisation of the A + T-rich region reveals the presence of the tRNA- and rRNA-like sequences and tandem repeats.
- Short tandem repeats are suggested replication fork barrier in insects for the first time.

Two complete mitogenomes of the stem borers, Calameuta filiformis and Calameuta idolon, and the complete A + T-rich region of Trachelus iudaicus (Hymenoptera: Cephidae), are reported. The mitogenomes of these species are the longest reported from hymenopterans to date. A remarkable increase in length of the A + T-rich region, the longest for Hymenoptera, was found and compared across the tribe Cephini. The presence of the tRNA- and rRNA-like sequences were reported in the A + T-rich region of sawflies and they were suggested to play a role in replication and/or transcription. The long and short tandem repeats were orderly located in both sides of the A + T-rich region producing stable secondary structures. We suggest that the short tandem repeats are likely to function as a replication fork barrier.